Why not just put the Greater Evil’s in time out?
Okay so we know the greater evils will always EVENTUALLY come back, but it seems to me that the first go around went pretty well with the exception of Mephisto. Baal and Diablo couldn’t free themselves, and the only reason Mephisto could is because he had a bunch of people around to corrupt. Why not just do a take two and put the soul stones in super random remote locations, all you have to do is not build a monastery or a temple around it. Go deep into a random cave system, get the stone nice and comfy and then abandon it there. It seems like it’ll work pretty good for a while.
Now eventually will they get found and unleashed by some random happenstance, probably, but that will likely take way longer than if you build towns over them. We have seen that they can corrupt pretty much anyone given enough time.