Second part.
Okay, I have this idea as to let the helmet/backpack represent how advanced the mooncivs will be (partly of course). So in the first era, you have this big backpacks with the big helmet as shown on the worker in my previous post.
With that in mind, I propose to use a SAM infantry unit like shown below (or bone the SAM infantry to another unit) as a city security unit with only the machinegun as weapon. Remove the launcher completely and put a big helmet/backpack on it. This would be the "warrior" of the earlier game so to speak.
As a first semi-military unit (remember, the mooncivs just prior to/just after Isolation aren't
that organized I suggest the grenadier-style unit shown here. Also give it the big helmet+backpack and make it slightly stronger then the security unit. So "mobs" like this have a fighting chance taking a base, especially if culture defense isn't so much an issue since this is not supposed to get high this soon in the game. Personally, I'm not completely happy with the fire effect on this unit's stick, but I guess I should consider it as an engineering torch and the unit a drafted civilian or something.
Except for the colonists, I think these 4 units are sufficient for the first era.