tl;dr: Freed slaves should be given their own states post civil-war so they aren't surrounded by their racist ex-confederate owners, waddya think?
Is it plausible for the Radical Republicans to adopt the idea of carving states out of the former confederacy for freed slaves? Basically new states would be created by breaking off majority ex-slave regions of confederate states and said state would be reserved for free blacks. Of course the demographics wont be perfect. It would be impossible to get the population of these proposed states to be 100% freedmen, but I imagine there will be a sort of natural migration of freedmen to these new states given incentives from congress (Education, land, political say, and the rest of the things the Radicals tried to pull off OTL with mixed success). Also, Ex-white confederates would likely move out of these new states not relishing the idea of being governed by free blacks.
The success of these new states would likely hinge on military force but that's not implausible given the willingness of congress to use a fair amount of it OTL. In the creation of these states the Radicals achieve alot of what they set out to do OTL, educate, employ, and empower the freedmen (politically). It also fulfills the much desired "punishment the confederacy" concept that was popular amongst the radicals at the time. Once the migration of blacks to free states and migration of ex-confederates out of free states dies down military occupation can start to be cut back. By this I mean the old confederate states can be readmitted with their mostly white populations with military occupation ended in those states while military occupation continues in the free states until the freedmen can take over from the federal troops.
Is the plan perfect, no, will segregation still be popular in ex-confederate states, yes, will KKK like atrocities still occur, unfortunately so. But the plan allows military occupation to concentrated around the people who need it and wont fight against it (unlike OTL ex-confederates) and gives congress clear locations to go about their OTL agenda of black enfranchisement.
So what do you all think? Any holes in the plan that you can see? Also what kind of POD do you think is needed, freedmen states seems like something the radicals could get on board with given the right circumstances. Perhaps killing off Johnson will help or have Lincoln pick a VP that becomes POTUS after his assassination who promotes the idea of free states and actively seeks congresses backing. The decision to promote freedmen states doesn't have to be an entirely well intentioned one mind you, there were many people back then who believed whites and blacks couldn't exist together as equals. Freedmen states could appeal to the idea of empowering free blacks while also appealing to the somewhat racist mindset of a benevolent segregation of whites and blacks via state boundaries.