The Lava Minining is probably like your suggestion, Freeza. I need to look back at it to make sure but I'm too lazy to do that now so I'll just describe the lava mining idea:
As lava is a relatively rich source of various minerals, a special mining unit could be used to break up lava into ores that could then be trucked to the smelters. While this will provide some materials, it will not be good for everything... You will need to have real mines in order to really provide for your colony.
I'm thinking, however, that cooled lava could be rich in rare materials so it might be good for that as a supplement to rare mining in areas with very low-yeild rare mines. It could also be used to help boost agricultural growth.
As far as repairs are concerned, Tokamaks will definatly need constant repairs but for the most part the structures on Bob will only need repairs after being hit by various disasters or enemy fire (or debris from a nearby explosion). It would add much to the complexit of the game.
However, just as a bit of eye-candy and to create a more lifelike feel and look to the colonies, now and then work-crews will just simply appear to do 'repairs' on structures. These repairs will be for minor things like a loose plate or a cracked window or any number of stupid things like that that you'll probably never really care about. It's the general maintenance of any structure and is not something the user would have to worry about ever. It just happens provided you have colonists in your structures. This effect would really only be available on higher-end machines (again because it could have a profound effect on low-end machine performance). Either way, picture it: A hatch opens and 5 colonists in environmental suits walk out. The climb onto the top of a structure and being work. The ones with Arc Welders will actually cast small lights and sparks will be visible. Damn, I think that'd be freaking sweet.
As far as ambient animation (like a hatch opening and releasing smoke) and that kind of stuff will very much be in the game. It's just too necessary to make the colony come to life.
Smoke will be a really neat effect. I've done some prelimary smoke demonstrations (to figure out the best and fastest way to render it) and it's looking pretty good. It'll be a neat effect.
Also, certain buildings when damaged may actually catch fire. If it's an Advanced Lab, for instance, the fire can actually cause it to continually lose HP and explode. So it's an added bonus/challenge to the game to make it more realistic... (thumbsup)