One thing you might consider is to have some restrictions on things away from earth when using civics that wouldn't be able to extend well into space eras, especially those that lie so far away that communication and enforcement becomes a problem. There are plenty of scify stories about distant planners not exactly agreeing with central government.
One option would be autobuildings that would spawn space barbarians, unless they were prevented in some way, such as by being replaced by other buildings possibly locked behind space civics (in which case they might also be autobuildings). Having to fight space pirates in some stages of space eras would both provide the opposition sorely needed in the later ages, and also allow one to go through the 4x phases again.
One option would be autobuildings that would spawn space barbarians, unless they were prevented in some way, such as by being replaced by other buildings possibly locked behind space civics (in which case they might also be autobuildings). Having to fight space pirates in some stages of space eras would both provide the opposition sorely needed in the later ages, and also allow one to go through the 4x phases again.