This will significantly limit humanity's ambitions to colonize outer space.
Plus, this analysis is implicitly in the context of a world where the regions have the ability to be self-sustaining on at least the basics of life, so breaking away is a viable option. If the "empire" is also "your supply of oxygen", breaking away will be a lot trickier. For a space colony or set of colonies to be able to break away, they first have to be truly 100% self-sufficient, and that's a tall bar for the forseeable future. They then have to be able to militarily match what the empire is willing to throw at them to retain them, and that's a very complicated analysis, made all the more complicated by not knowing what the exact technologies will be at the time.
(Plus, not all empires are complete buffoons. They at least begin being competently run. The empire will know that to break away the colonies must be self-sufficient, so they will take steps to ensure they won't be self-sufficient. And the colonies will take steps to become secretly self-sufficient. Long before open rebellions occur, there will have been a clandestine war of self-sufficiency.)