This is far too ambitious a project for any individual, and I'm not sure I'm the right person to lead it, but I'm sketching out a design document for an Alpha Centauri total conversion in the spirit of Planetfall. Starting premises:
1) SMAC is "about" modern-era ideologies struggling in a world they weren't designed for, literally and metaphorically - how their traditional struggles play out against that backdrop, how they actively shape it, creatively respond to it, and get overwhelmed by it.
2) Unique, nonzero-sum win conditions for each Colony based on the ideology of its associated Faction - for instance, the Stepdaughters preventing a certain threshold of environmental damage being reached. It should be logically possible for no, or all seven, or almost any combination of players to win; they are still driven to conflict, of course, by the existence of scarce resources and by the fact that optimizing for one thing entails not optimizing for another.
3) Separating pop Faction identity from Colony Faction identity using the Religion chassis. With Faction features at the base (city) level keying off of citizens rather than player, tradeoffs arise between a loyal population and a diversely capable one.
Hopefully the full draft will make a compelling case for why these, and adapting some other mechanical chasses from recent iterations present in VI, could be the foundation for something both thematically resonant and strategically interesting, even if some of the details have to be extremely hazy at this point. (If and when I do finish said draft, would it be more appropriate in this thread or one of its own?)