This guy, I like. 
Re: Researching Plasma Weapons
As I’ve admitted, my memory’s spotty on this, but I think you do need to research all of the hand held plasma weapons before you can research the ship mounted Plasma Cannons. Quickest way to tell is to research one (preferably the Heavy Plasma) and a clip for it, and see if Plasma Cannon shows up in the research tree, when you’re done.
Once you’ve researched a given type of weapon and the ammo for it, you’re able to manufacture said weapon/ammo, provided you’ve got the raw materials (Elerium and the Alien Alloy) on hand.
I always found it easiest to just use laser rifles until the endgame, for the weight/monetary savings on the ammo. In fact, unless you run across some heavy opposition early on (easy to do at the highest difficulty levels) you really never need to make any plasma weapons, as the amount of them you’ll capture are more than sufficient for your use.
Of course, I never had much respect for “collateral damage” to existing ground structures, with the exception of cities in the terror missions, so I needed the unlimited ammo capabilities of the laser rifles to cut down the buidling around a dug in alien, anyway…
“Sarge, there’s a Floater in that barn, and he’s killed two men who tried to approach the building.”
“Has he chucked any of those pocket nuke grandes at us yet?”
“No, sir.”
“Well, taking him in a rush isn’t gonna work, then. We got any heavy explosives on hand?”
“No, sir.”
“Well then, set up a firing line of six men with laser rifles, and burst fire the building down around him. If the falling debris don’t get him, someone’ll spot him eventually.”
“And then?”
“If the guys with the lasers miss, light his ass up with some incendiary rounds from that hand cannon you’re carrying. That way, we can see him better in the dark.”
The governments loved me, but the farmers, not so much.