Well, in theory an MU exists for every choice we make for the choice we didn't- so there are probably lots of MU borg... I don't think the fans will find it offensive- they'll have new respect and pity for the Borg, maybe be more sympathetic, try to help them, won't feel so overwhelmed... or maybe blow them up, who knows... I wouldn't be offended- kinda hard to shut those doors completely...
It's just that...after all this attention to the final, irrevocable end of the Borg, I would hate to have them brought back again in the MU. The Borg should end there too. Although, given the general state of affairs in that universe, *their* Borg will probably be dealt with more ruthlessly than these Borg have been.