Corbyn is part of a trend toward political diversity. That's largely why I want him to stay - if Douglas Carswell wins the UKIP leadership then that gives us a party in each corner of the political compass, and one near the centre. Compared to a decade ago, when everyone was clamouring for the "Centre-Right" sweet spot, that's an incredible change.
Labour's history and Union backing makes them the natural Socialist party in the UK. If people want 'New Labour', or something similar to it, they'll find that in the Liberal Democrats. I'd suggest that many Labour MPs, and many Labour voters, would find a better home there.