I think that if the rift between Kim and Thurston is irreconcilable and that their musical partnership must be dissolved along with their marital bonds, the best way forward is for Kim to put her efforts into Free Kitten full time and for Sonic Youth to hire EMA to replace Kim. Check out her Daytrotter Session and her Nirvana cover (of "Endless, Nameless", the hidden noise track from Nevermind). She can play third guitar, and if she can't play bass, SY should just keep that guy from Pavement around, or some other bass player.
Then, as Thurston, Lee, and Steve each decide that as they age, they're ready to take some time off, find other similar talents to replace them in the band. Over time, we may have completely replaced the members of Sonic Youth while still keeping the band together. The band will actually have a chance at outliving its founders!
Do you think this will work? Will EMA fit into the band? Will SY drop Thurston instead, when there's no clear replacement for him? Can the guy from Pavement sing in place of Thurston? Will you give us your random ten?