I had a planet, which had a satisfation rate of about 45%.   In order to bring up my satisfaction rate, I loaded up people in colony ship.  Diminishing the population uncreased my satisfaction rate however even with a satisfaction rate of 100% my planet switched civilization (to the Altarians).   ( Perhaps less population means less influence ?)

Now my planet switched back at some point and when my planet switched back, it had Altarian ships in orbit which were not expelled from orbit.  I couldn't expel them myself so I ended purchasing them to be able to get them off my planet.  Prior to purchasing those ships, the Altarian ship presence in orbit prevented the colony ship I had created from being able to leave.

Starbases:  In order to be able to build influence starbases near Altarian planets, I first had to remove their starbases.  I did that by purchasing them and decomissionning them. Two things didn't go quite right with this scenario.

  -  The purchased starbases, kept their original colors and protective fleet.  For example my color was a brownish yellow, the Alterian is Blue, and it stayed blue.  ( I was still able to decomission the starbase, but I could easily have forgotten that starbase was mine.

  -  Unlike with ships where I can upgrade from one type to another providing they are the same size, you cannot do this with starbases.  The only option is decomissionning them.  It should be possible to upgrade the starbases to another purpose by removing the Economic / Mining / Military ring leaving the modules which aren't specific to one of those 3 rings.  This way a purchased Economic starbase could be converted to a mining starbase.   It's expensive enough to get those things in orbit, that re-use of modules is what makes sense just as you have with the ships.