I think it was boring about before game mode, you can make a new game mode, and I make a idea for the new mode:
There had many creeper on the ground, so there isn't have space to keep base. It will have a big gun in the space at the mission start and it is launching for a small space (because there is a few energy) to give a structrue space, and then we can place a weapon
And it is the rule:
1. All the strutrue must build in the space and fall to the ground.
2. All the energy is collecting from the ground by the spaceships.
3. Collector can make some energy by itselves (but it is less than before).
Hope my idea will give you much help. ;)
4RPL is your friend, then...