This is just an idea for the devs.
Labor should be a good purchased and sold on a market, in units of Pioneer-hours, Settler-hours, etc. It can be transported to a planet just like a good. Housing is a factory that takes food as inputs and outputs Pioneer-hours or Settler-hours, or higher tier labor.
This way, you model a labor market, without having to make a specialized population migration system. You just let the market (the players) decide the price. Labor does not need to live on the planet it works. They can commute. If you want to avoid the idea of labor commuting then labor consumables like RAT, DW, should be light and inexpensive to transport but pioneer-hours should be expensive (very heavy/high-volume) to transport.