A Khan (from Star Trek) Miniseries? Maybe so. Could be cool. There have been a couple of novels and comics that told this story (what happened to him and his people between Space Seed and Wrath of Khan) and I liked them.
Can’t we have light, happy Star Trek? Not picking on you, OP, but does everything need to be “dark”? I’d rather have a Gary Seven series.
Note that I have read The Eugenics Wars, and for the most part it was good. Might even make a good movie or two.
Maybe we need a Col. Green series? Or Kahless? 
I don’t think the time between Space Seed and WOK would really be all that sustainable as a story. I think there’s only so much you can do stranded on a desert planet with an evil superman as the primary protagonist.
I think they should look at Assignment Earth and work on an updated series for that. AE was a backdoor pilot and I think the concept is adaptable to a modern day stories. Have an Earth guy who is receiving missions from benevolent aliens working to shepherd us silly humans along until we’re ready to reach out to the stars. Have stand alone type episodes but have an overarching season plot. Maybe have a bit of time travel but stay the f— away from the Temporal Cold Wars, hint at Star Trek concepts and its universe but don’t lean on having Borg in 2017 Earth or anything too outrageous. Maybe bring in Khan and “update” the Eugenics Wars. SFX wouldn’t be too expensive, I imagine, since it’ll be set now but with some CGI and fancy gadgets. Maybe introduce another alien race that’s not so benevolent and pit the Gary Seven against them and their human representative, maybe have Gary question which alien race is really right. With more stand alone-type eps, they’d be able to do a wider variety with topics leaning from lighthearted to more serious stuff. Yeah, it may be a little Doctor Who-ish, but it will be set in the Star Trek Universe and Gary Seven will be more of a troubleshooter type with a little more knowledge than a manic know-it-all with a time traveling box (and I like Doctor Who, don’t get me wrong).
I agree that we want, nay need, a bright optimistic Star Trek. I am hoping that is what Discovery is, but as a secondary mini series this could be interesting. Col. Green would also be great. I think they are going with the known property but if it succeeds, there could be more.
ETA: there is definitely meat to the story. A novel and a graphic novel have both told it and told it differently.
I glossed over the part about it being a limited series. I think in that form it would work and I would also imagine that they’re looking to expand the Star Trek universe and franchise similar to Disney’s efforts with Star Wars (Rogue One, Han Solo, etc.).
I’d see it. I can’t imagine subscribing to All Access and I think Assignment Earth or something between the TOS movies and TNG would offer more, but I would support it most likely like it.
If you haven’t seen these, they are interesting. Might not be adaptable to TV, but worth a read. The first is Marla McGiver’s personal logs on Ceti Alpha V.
The second is the story’s aftermath, from Khan’s POV:
I’d like to see something a decade or two after DS9. It ended so abruptly with lots of questions and potential story directions.