There would be no military units to speak of in this era or colonist units. Just engineers and espionage units.
1 hp security units are almost a must.
You would start with access to radar, radio and power towers/stations (buildings) and radar, radio and power relays (improvements). There would be no culture generation. In my view, culture represents your civ's influence on the ambient population. There is no ambient population on the moon. Instead, culture represents your power grid (which is why you can only build improvements in your cultural radius). Depending on the size of your generator and infrastructure, that determines your city's cultural radius. Your power grid is extended by power relays. Radar controls your view range, as well as providing units under radar coverage a bonus. Radio would provide your units with an in communication/incommunicado bonus. Early scouts couldn't move out of your radio range (and remember there is no atmosphere to bounce off of), because they are unmanned. Units in radio range also gain a withdrawal bonus.
Sounds good in general. One remark, a simple relay satellite (or a chain of them in orbit anyway) offsets this "no radio outside territory" range thing. But that could perhaps be acquired from a colony's home-civ.
Terrain would cause attrition scaled by tiers (out of power grid radius, out of radar range, out of radio range, with a special multiplier if just revealed). Attrition would represent small amounts of damage, limiting your units ability to go wandering off. Mechanical units which attrited themselves to death would leave salvageable wrecks that could be recovered by salvage teams. Similar the map would start with a series of goodies--impact craters, crash sites and salvageable probes and rovers. Salvaged units could be reactived or converted to production/coins.
Wonder if it is possible to link different graphics foor all these "goodies".
While contact with Earth was maintained, similar to Colonization, you would be able to request reinforcements from Earth. New specialists could be hired, as well as additional materials, convoys with food/production on them, building kits, etc. Availability based on contracts negotiated (researched) contacts assembled, commerse rate, civics, civ faction and difficulty level, and would be purchased with gold.
If you could program that "free specialists" provide food/hammers/commerce only when certain resources are linked (ie. He³, minerals,...). Or else that a free specialist providing food and stuff is put in the base screen once a plot is worked with a resource Earth "needs". (He³ again)
I would not necessarily have facilities that are dismantled once the survival era begins, but more like facilities that are based on research/mining that lose the part of their benefit that represents what Earth wanted out of them. For instance a far side of the moon observatory, a linear particle reactor, the electromagnetic launcher. Some (or even most) of the He³ commerce income, water ice -and oxygen plants. Make the 3 facility examples I gave a national wonder. So everyone colony can build them only once.
With the slow(er) building times in the early game, not that many normal facilities are needed. One basic one that comes to mind is a "dust cleaner" to clean surface suits/vehicles when their occupants return to base. The fine moondust surely is a health concern in the closed habitats of that early age.
Another one that comes to mind is early radiation shielding (even if it is only a meter of rock material on top of the habitats).
But in any case Belizan, you're talking about a truly rewritten tech tree here. Not sure if Woodelf would be happy with that.
