First, we do intend to put something in as a "civilian" space station, however income will not be the primary use. As for other military stations, XQs would most likely only be used by a select few factions, though I do intend to put the one in from Ascendancy for certain of them (we actually do have one that's already in ICW, but it was cut years ago for a few reasons). Trade stations will only be used if we can actually make Sins-esque trade mechanics work.
On the ground, there could be more difference in income. OK, I know there are already two methods, but the only difference between the mining facility and the Tax Collection Agencies are minimal... Well, except for the Hand.
But 5 imperial factions having the same TCA is not the best idea...
Also for the other warlords there could be some minor but more important difference in the Income, like Zsinj using TCAs, but cost slightly more, limited to 4/planet but would give a slightly larger bonus, while maldrood's being unlimited, cheaper but give a much smaller bonus.
Eriadu could use Mining Facilities for sake of some difference, but with different parameters from the NR's and Hand's version.
This is where we run into difficulties. Having a single consistent Tax Agency situation among the Imperials (or giving one or two the Mining Facility) is much better than making even smaller artificial differences between the factions within what's essentially the same building, unless it were something like a "Corporation" you could build for the PA. The name difference brings at least some aesthetic variation to what's happening, and we can attach slightly different stats to it with a clear indicator of the fact that those differences exist, even if they're not huge. If, between the IR, Maldrood, Zsinj and Eriadu we tried to make it so they all used tax agencies, but the IR one was 10% better than the Eriadu one... Well, why? And how can that be communicated clearly? And who would notice? It doesn't really add as much for seasoned players, and for new players it's at best a non-factor and at worst confusing. Most likely the end result will be Eriadu, PA and maybe the NR with a new Corporation building (or trade if we can make it work properly), IR and Maldrood with Tax Agencies, and EotH, Zsinj and the Duskhan League with Mining Facilities. There will be slight differences within those buildings, but between the factions they will be the same.
Primarily my concern as far as space stattions go, though, is fixing the shipyards so they don't make battles where the AI is defending so terrible.