I also agree that the plan is a little vague at this point. There are a lot of layers to Apocalypse and a few more layers that they cut or only partially implemented due to time/funds. Getting something with so many small modules balanced will be no small feat... but that's no reason to stop trying!
I, personally, enjoyed Apocalypse more than Enemy Unknown. Its real-time offered an enjoyable mix of strategy and action. i agree with All Names Taken that trying to implement both as they did is probably making this undertaking start to get out of control.
Some things I would like to see in a game like that would be an Ironman mode where it autosaves to offer an option for not being able to save-reload repeatedly. In the actual gameplay, having to manage so many details of your base was a fun experience but I'm not sure how today's gaming audience would feel about that level of depth (like hiring individual engineers and scientists; deciding to send troops to psy training vs combat training). Having lots of subtle and not-so-subtle value-adds tied to the various city organizations is a great touch. Like how Gravball League contributed some very able troops which served as an incentive to stay on good terms with them. Like how Megapol and Marcel both supplied various weapons and armor so you wanted to stay on good terms with them so you could access their goods. Like how the taxi group ensured you got your troops, scientists, and engineers to your base quickly, but if you fell out of favor with them, you'd have to rely on the tube systems which were slower. Just so many little reasons to keep a given organization on your side but not reasons that meant you lost the game if they became hostile. Again, that won't be an easy thing to balance. But the payoff can be quite phenomenal when it all comes together.
I think if you get those finer points right, the fun factor will be there and people will be quite flexible on if you're presenting it as a city or the Earth or some inter-planet coalition or whatever else you might come up with.
I would definitely be interested in playing something along those lines. Have fun bringing that to fruition!
A link to some of the interesting aspects that were cut from Apocalypse (http://www.strategycore.co.uk/databank/games/x-com-apocalypse/concepts/).