Star Bases that have combat but no strategic movement are already possible. I have included this in my mod (1MP max). Made a special Station Keeping Engine for bases only (similar component could be made for satellites too). Only problem with these moving bases/satellites is that AI tends to attack with them, leaving the planet defenseless against smart player
.
I have been searching the files for a way to limit bases movement on planets orbit, but atm i think it's not possible.