Well I would go as far back as I could, fixing inconsistency's wherever possible, making the universe more streamlined if you will instead of a patchwork of fluff which may not work always together, or perhaps do but are a bit haphazard in application.
A more consistent art package might be nice, perhaps each faction having it's own style, or perhaps not?
A more consolidation of the number of units however would be nice, while the main draw is the TROs, however it seems its difficult to tell if a unit is actually replacing another unit in service. Though this dose not necessarily mean the replaced unit should get completely replaced right off the bat, it could go to militia or mercenary or even pirate use for a time.
Though unit design for some units should improve, for example IIRC large aerospace units could differently need some improving, IIRC you (Herb) mentioned once that current warships are "so bad" that it makes it difficult to place a older design to that ship in universe...
The industrial and military size is one of the more broken aspects of the B-tech universe in the game, this could be improved, though a true fix is not realy needed however even a partial fix can be useful.
Well one thing I would like to see put to rest is the notion that depending on your view point current day military vehicles could easily beat it's B-tech counter parts. It's kinda jarring to know that depending on your view it's possible that the B-tech unit around could easily get defeated by a unit that was technically made 1,000 years ago in B-techs past, and this dose not even have to be along military lines, you can look at civilian vehicles, electronics and what naught...
In some ways this is part of B-tech flavor... So I do not think we need AIs, anti gravity, and what naught, but what B-tech dose have should be made a bit more clear that it while perhaps not as flexible as current tech it at lest dose what it dose a lot better than what we have, or at the lest roughly equal in capability (I have found a number of references to gigabyte and terabytes in the fluff for instance).
Also better attempts to explain why some things are would be nice instead of as some guys I know would say as badly done half-arsed attempts.
One example is it seems even though it's said that the ranges in game are their for play ability reasons and not necessarily what they could be in the B-tech universe but the fluff still uses them like crazy! So which is it?
Edit:
Another thing I would like to see changed is the notion that the Gauss Rifle fires a large spherical nickel iron cannon ball, to something else...