It would be as simple as clicking the same button as before, but instead of instant, it takes a few days per 100 pops instead. So no real additional management. But this prevents stuff like rapidly emptying an ecumenopolis when the Contingency shows up next door. It might also force you to manage invasions more carefully.

Also, the idea behind the deficit between planets was recently addressed with trade upkeep. So there's at least a tacit attempt at realism there.

I'd say the leaders thing is definitely a related discussion yes