Some suggestions.

[andriusha]

Mobilized defence:

Sentry turrets that can patrol around the map, and be controlled by the player, it would make it possible to fight off riders with them, without any colonist casualties. Each turret could be controlled by a colonist on a control panel or something. While the colonist is controlling a turret, he will be unable to do anyhing else. If the controling colonist leaves the control station, the turret will return to its default location, or wander/patrol around. When the turret is destroyed, the colonist could get a mental debuff. A turret must be refueled at a cistern or a cannister. (Read below).

Fuel:

Maybe some oil puddles around the map, that could be collected with a special building. The oil would travel inside Pipes (Like electricity in power conduits) to a procesing building to make it into fuel. Then, the fuel could travel with another pipe to a canister or a cistern (Like batteries for electricity).

Fuel Generator:

This one is simple. It would convert fuel (read above) to electricity. Easy as can be.

[Finn]

Gotta say, these ideas seem really sweet.