Factorio-ish set in the SMAC universe (with Hints of Anno and Creeper World), loosely inspired by
Sirus' post in the Factorio thread
You lead an independent team vying for contracts to protect settlements from the native fungus life. This predominantly involves building defenses around cities to protect them from mindworm incursions (all varieties, land, sea, and air), but also includes pushing back the fungus (Creeper world; fighting fungus towers ) and harvesting resources outside the cities because it's too dangerous for citizens to do so. Possibly includes production chains for producing your own equipment, and research chains so you can develop better equipment. Tech period would be late game SMAC; all of it is technically researched, but no faction has "won" the SMAC game. Most tech is only readily available to the factions, your research is in developing "in house" methods of production for your own use (may also allow trade with factions for this).
Scope is wider than Factorio, you wouldn't be just one guy, but I'm not sure how to best manage legal (gameplay-wise) construction sites. Maybe set up (and supply) "outposts" and those outposts allow constructions in their influence (Anno warehouses)? Any given region will probably have a mix of faction cities and you can negotiate with any of them to provide them with security and resources. Contracts with cities (independently cities, even if they belong to the same faction, but there might be bonuses or penalties involved there) are your main source of... probably not energy credits (since you could just build your own solar collectors) but $currency. The general SMAC gameplay takes place between AIs above the scope of your own game, so factions might not like you negotiating with their enemies, and possibly having to get involved in a versus-human-units vendetta. But that's just to offer a great variety of scenarios, preferably with a robust random map generator to maximize that. Oh yes, and you're not the only team out there; there are rival contractors, your main goal is to become the de-facto fungus contractor in the region by either eliminating the rivals ("Sorry chap! Hazardous work out here!") or securing long-term contracts with most of the cities in the region.
I'd want the scope to be wide enough that the cities are present in the region, but that might be too wide. It could work okay for the Hive, whose cities are mostly underground, but the rest of the factions would probably end up being "cities" like in Skyrim or MMOs: tiny because the virtually the only buildings present have a purpose, with nary any space for the thousands or millions of bodies most cities need to actually get through the day.