this is the maximum extent of russian annexation that i would support on purely democratic grounds:
however, this map would be impossible for russia to defend from an attack by germany, which is their justified concern. hitler and napoleon both tried the same basic thing, and they both failed. if the russians don't have a way to protect the massive flat land they exist on from attack by germans or franks, it will happen again.
a better idea - and i haven't talked about this in a while but i've been through it - is to try to split the country off at the dnieper. this map has this major river running through it:
the river is not impenetrable, but it provides a natural barrier. i'm reminded of mccarthy starting the korean war by getting too close to the yalu river, which the chinese told him not to do. mccarthy got too close, and the chinese pushed him back. the russians could conceivably use the dnieper the same way.
this would require occupying an area of ukrainian speaking territory and abandoning an area of russian speaking territory, but the next river is the vistula and while that might be better, it's also impossible.
if the russians were to hold the areas of ukraine east of the dnieper, it could arrange population transfers, like was done between greece and turkey. the greeks left ionia and went back to attica. russian speakers could transfer to the east of the river, and ukrainian speakers could transfer to the west of it.
the major reason the russians haven't been able to do this is that they won't bomb out the bridges over the dnieper. the ukranians have bombed the bridges to prevent a russian advance. the russians refuse to bomb the bridges that the ukrainians are using for supply lines. if the russians would just take the bridges out, ukraine would be unable to supply it's troops on the other side of the dnieper, and this would end very fast. my understanding is that the russians refuse to do this because they think it's barbaric, and because they think they don't have to.
this would be over by now if they had done that. without supplies, ukrainian defenses would quickly collapse and the russians could move to occupy the area east of the river with relative ease. ukraine would have to surrender. that also means the russians couldn't get over the river to take the rest of the country.
these considerations should no longer be seen as realistic. barbaric or not, if the russians don't take these bridges out soon, they could be dealing with a substantive counterforce intent on using them not just for supplies but for soldiers. they should have done this years ago. they no longer have a choice to pretend they don't have to - yes, they do have to.
this is a realistic way to actually end this. ukraine will need to accept the reality of heavy russian fortifications on the dnieper. however, the flip side of that is that ukraine itself doesn't need to be in nato to act as a further disincentive against russia. the fact that there is no geographic boundary west of the dnieper until you reach the carpathians and the vistula, both in nato, is good enough.
the next step would need to be the russians pulling nato out of poland, first. it would be pointless to continue a war against the western part of ukraine, with no geographic boundaries in ukraine that can provide them with position. the position they seek is the dnieper.
if the russians were to keep pushing further west than the dnieper, i would join the side arguing they need to stop. but, they won't.