Oh yeah - I forget what the name is, but when we had our 2 shower stalls installed, there was a special kind of system for the pan to prevent leaks. Possibly Schluter? The general consensus was that it was far superior to older generations of shower pans. Might be worth a little research.
Just remembered we had a bidet thread not too long ago.
Sorry, you said you had some extra money, so I thought, why not?
Glass door, sure, it’s probably better than a shower curtain. But I got two whole walls of glass in my shower, and that’s what I was advising against. All the remodel porn on TV has glass-enclosed showers, I just hope those homeowners can afford a maid to clean them.
On the subject of aging in place, a walk-in bathtub is a wonderful thing. Its not just an accessibility issue. When your joints and feet and muscles begin to ache, a good long soaking bath is the best relief you’re gonna get. If you can’t fit one in as well as the shower, consider adding it to another bathroom while you’re doing stuff.
Since the room is small, consider how much added space you might get with a pocket door, or even just a door that opens out instead of in.
I like a functional sink. If I were doing this I’d shop for sinks and faucets in the kitchen department. I can’t even fill an iced tea glass with water at most bathroom sinks these days. It’s ludicrous.
I’m team “no glass.” But I hate glass in any form. I knew an elderly woman who kept her house quite cold in winter time. She turned on the shower, the heat hit the glass and it shattered. No. Glass. If you must go that way just get acrylic. It’s cheaper and it won’t try to murder you.
Heated floors and towel racks. Its a luxury now, but will vastly increase your comfort level as you age.
In a small room, every inch of drywall is wasted space. Recessed cabinets are not just for medicine, you can recess space for linens and anything else you might wish to store in there. You are going back to the studs anyway, so go for it! (Another “as you age” thing;:adult diapers etc need big cabinets. Give yourself the gift of a private place to keep them.)
Can you put the sink outside the bathroom? I’d do that if I could. I HATE having my toothbrush in the same room as the toilet.
This one is the wrong size, but is the ceiling height enough that you could fit a pull-down clothes drying rack above the tub/shower?
Bidet - when your back goes, it will save your dignity.
Used to have a nice from this room before I bricked up the windows! 
Ceiling mounted (or rain) showerhead. At a minimum run a wall based head up to where it comes in close to the ceiling. It may be less of a big deal since there’s not a tub involved taking up a couple inches but I’m tall enough that a lot of showerhead placements require me to crouch a little.
It’s probably not most people’s dreams though. I get that. 
The real thing that would make a master bath perfect is someone else to clean it - because I really, really, really hate cleaning the bathroom.
After that, mine is about the same size as yours. In my dream bathroom remodel, I’m getting a standing tub (one of those ones for old people, because I will be old someday). I’d also like heated floors. And a Japanese toilet. And storage. Lots and lots of storage. I have mixed feelings about getting a “smart mirror” because on the one hand, they seem stupid, but on the other hand, they feel like something I might really want in 5 years.
Preach it, brother.
The shower in my (otherwise fantastic) bathroom is a full glass enclosure. Super pretty. Everything else, tub, sink, floor, is white. It’s nice.
But oh, God, cleaning it.
What I ended up doing is keeping a squeegee in the shower, and squeegeeing after every shower. It’s not that big a deal, really, but I feel like I shouldn’t have to do that before I get out of the shower.
I know, first world problems.
This is timely. My major bathroom remodel was completed last week. We even moved a wall to enlarge the space.
Think 3…no, 4 times about electrical outlet placement. We only thought thrice, and sure enough I am already planning on adding one where I now know I need it.
Grab bars are not a bad idea, whether you are disabled or able bodied.
We put a built-in seat at the end of the tub because there was room. I don’t really see myself using it, but then I don’t shave my legs.
We were very minimal with towel bars (none), alcoves (none), soap dishes (none), and anything else that can act as a ledge for crud accumulation.
Make sure that every water pipe has a dedicated shut off.
I wanted a medicine cabinet, the boss wanted just a mirror. We compromised and bought a recessed cabinet that makes us both happy. It wasn’t cheap, but we are so happy we sprang (?) for quality with this item. It’s my favorite decision.
Good luck!
mmm
My small house was a custom build by a guy with many unique ideas. Things he did in the bath were:
[ul]
[li]Tiled in (Roman) tub/shower[/li][li]Skylight above tub/shower[/li][li]Kitchen cabinet height (36") built in vanity with tiled in sink.[/li][li]All walls outside shower are mirrors[/li][/ul]
First three are great - the fourth I like but it shocks people. Makes the bath seem larger.
Waiting to have time to reply in bulk, but re: mirrors. Lovely wife wanted a BIG mirror. I was thinking about making that entire side of the bathroom a mirror, either two recessed medicine cabinets, or a cabinet and a mirror. Then today, I thought…hey…what about a recessed, mirrored cabinet on the opposite wall?
That would result in all walls that aren’t shower or window covered in mirror.
Add me to the chorus. Keeping water marks off the glass is a pain. I’ve used Rain-X or similar products to help reduce droplets, and then I squeegee after every shower. It may be a first world problem, but standing there shivering while you wipe off the damn doors is not the best part of my day.
I hate the glass doors. We had the frosted ones and it was so hard to keep them clean. They looked awful after awhile. And cleaning the tub from the outside when there is a door of any kind, is sort of painful. Those rails dig into you when you have to give the tub a good cleaning.
My bathroom currently has no electric plug. Don’t do that. 
I like to have a tall storage space for towels and spare paper and other stuff.
Have fun! Take lots of pictures of the progress. That will be fun to look at later.
Also take pictures so if you have to open a wall to get to something, you know exactly where to cut. 
You do realize who the OP is & why his user name is that, right?
I vote for heated floors; not necessary, but oh so nice. However, extend them a bit. My cousin’s house has them. The one wall is shower, tub, & toilet so the heated floor stops at a common line of the shower & tub. Let’s just say I literally get cold feet peeing.
Glass walls don’t have to be a problem. Clear glass is a hassle to clean. But get clouded glass, and you don’t have a problem with water spots and calcium buildup.
As for showers, get an external shower head with a removable handheld spray nozzle.
Like this one:
They come in silver or brass colors and are quite attractive.
The head works as a regular shower, but you can adjust the height, and also lift it off the hook, and hold it in your hand to spray water at specific spots where you want it(or don’t want to get wet). Useful if you ever have to shower while ,say, wearing a bandage. Or shower without getting your hair wet.
Also useful for couples who are not the same height 
But this is also important for the (previously mentioned, and dreaded) aging-in-place scenario, or just recuperating after surgery. One day you’re going to have to shower while seated, possibly in a wheel chair.
Yeah–grab bars should be installed now, not some day when you’re in pain and being transported home from the hospital.
And definitely design with easy access, wide doors for a wheelchair.
I’m pretty sure that shower door glass is tempered, so if it shatters, it’s not going to make dangerous shards. As for frosting the glass to hide water deposits, the problem is the frosting makes it harder to clean than smooth, clear glass. Perhaps not an issue if the outside is frosted, and the inside, closest to the showerhead, is not. And I think there are coatings that help prevent water deposits. The installer can advise about the options.
I did not: up until now I had assumed it was a play on the joke about “seven ate nine”.
We did a large master suite renovation a few years ago including an all new bath. We had much more space than you do but some ideas we have not regretted:
Electrical - Two things we did that are super helpful. First of all we mounted two electrical outlets in the mirror above the vanity (we have double sink vanity) and they have mirrored outlet covers and look very nice. So now my wife has a convenient and easy plug-in for hairdryer, curler, etc. where she gets ready. I have one too but have never used it. Haha. Secondly, we also had electrical boxes installed inside the vanity storage space on each side. My wife could plug her hairdryer into that box and then store away the hairdryer when she was done but that would make life more peaceful and sane for me so instead it stays plugged into the mirror receptacle and sits on the counter all the time. Ah well, I tried. BUT… the best use we’ve had for the receptacles inside the vanity is for things like charging stations for our electric toothbrushes or my beard trimmer. They can be plugged in and out of site and when a toothbrush needs a charge it’s inside the vanity cabinet and not on the vanity top with an unsightly cord.
Fixtures - Don’t go cheap here. Go to an actual bath/plumbing store vs. a big box chain. We used high end fixtures in our remodel and you can tell the difference in look, feel, and operation. Like men’s attire, the finishing details make the difference. You’re only going to do this once so why go cheap on the items you’ll touch and use every single day.
Shower glass - We don’t have bad water and we did frameless glass and I love it. Our shower is very large (4x7x10) with double shower fixtures and all marble. We have made it a habit of using a squeeje (?) after every shower including the door. Takes less than 30 seconds and we have not had any issues. Note there are different grades of glass for this purpose. I forgot the details and don’t have time to look it up now but basically one will have a blue/green tint to it, the other will look as clear as… well… glass. Get that type.
Water Closet - It doesn’t sound like you’ll have room but we isolated our toilet in a water closet with a door. For one, a toilet is rarely a visually appealing element in a design. For two, it’s nice to have privacy. As my wife says, “I don’t ever need to see you on a toilet ever again”. She’s a great woman, really.
Heated Floors - Didn’t do this in our current home renovation but in my previous home I did and was the single best thing ever, especially if you do a tile floor like marble. In the winter there is nothing better than warm stone under your feet in the bathroom in the morning. Small thing, not a lot of extra cost, but so worth it. I recommend installing two temperature sensors if you do this. One you’ll connect to the control module/thermostat, the other you just leave unconnected and the wiring in the wall behind the panel. That way if for some unlikely reason the temperature sensor goes bad, you don’t have to rip-out the floors to replace it you just simple disconnect the dead one and connect the other. Yes, that saved me a lot of money.
Bidet - I wanted a separate bidet. I didn’t get my way. So do it if you have the space and interest and think of me.
MeanJoe
I don’t get all the talk about cleaning glass showers. We had one for 5 years in our previous house. Sure, they got a certain amount of soap scum on the inside, but I think we washed it off maybe once or twice a year. (I don’t recall anything more objectionable than that.) Neither of us found it particularly bothersome, and we each liked being able to see the other in the shower. 