I would like to have this.
I would implement it in the way that populations would drift naturally, but you could also use some kind of focus and policies (e.g. Homestead as you mentioned)/ to encourage/deter migration to specific planets,
Perhaps a planet has a good base for strong industry, but lacks POPs, you could have a dedicated farming and growth planet, and then move excess population to the industrial planet, or where-ever you need them.
Also if you want to be evil you could conquer an alien planet, and then migrate your own population there to effectively wipe out the local culture and perform "russification" as it were.