[thejeff]

That actually avoids the easy problems and ignores one of the others.
As others here have said the preferred way is to use the old files for as many players as possible to minimize the chance of people acting on info from the problem turn. Your solution doesn't allow that.

More importantly the most significant chances of corruption come from the client side, when someone plays the next turn without deleting the .2h he started with the problem turn. There's no way for the llamaserver to force the player to make a new savegame directory.