Population Immigration Between Alliances

I often play a custom faction designed around The Borg from star trek (Riftborn with the Gene-Splice Affinity) and when I play with a friend of mine I'd like to be able to request or offer to have some population Immigrate between the two of us when we are allies via the diplomacy screen. I want him to send me samples of populations I don't have yet and I want to send him populations I have already spliced but cannot get rid of (due to the lack of the Horatio improvement which swaps out a minor for a major).

This would also allow in slightly longer games for players to really optimise which minor factions (or major factions) they do or don't have in any of their given systems. Playing Lumeris with a Riftborn ally? You can send them all (or most) of your Haroshem in exchange for their Kalgeros since you're both terraforming in the opposite direction.

I would mod this in myself - 

1. somehow get the option into the diplomacy screen
2. likely force a population to leave
3. create an exile anomaly event at one of the sending faction's planets to the receiving faction

- but I'm new to modding and I don't believe the necessary data is available to the public folder to feed in a list of the faction's minor population.

Things to consider:

• This should (maybe only "could") require an improvement to do. Something like a child tech of perfect negotiations in the following era.
• Only the populations on a system with a starport can immigrate inter-faction.
• Immigration requires starport slots to be used for the turn that they're initiated
• The number of population immigrated, the origin system and destination system are defined in either the diplomacy screen or they're defined in the starport(s) of the origin system which produces an "immigration ticket" inside the diplomacy screen which costs influence proportionate to the amount of population being moved. The tool-tip would describe which populations are moving from and to where.

I don't believe that this would be a difficult system to implement and I could do it myself with mods with just a fraction more information available to me via diplomacy.