I would love to see TAS re-animated. If the original show, which are far more sacred cow anyway, were upgraded in SFX, why not TAS? It'd sure help bring more validity to this little-seen Trek show.
That said, it probably won't happen. Too much cost for something that is, as said, little-seen. Maybe
try out one or two episodes (certainly Yesteryear and the Tribbles epi), but not more.
But I would like to see though, is some touch ups on the animation and background. Significant enough that it'd look sufficient for a blu-ray release.
Ideally, the blu-ray of TAS would include touched up - improved episodes on the existing run, and an addition of the scrapped Secrets of the Vulcan Fury retooled as a six-part arc (yeah, I also know that won't happen, but thats why I said ideally, too).