Even if Clinton had the backing of the Democrat party, with fundraising and such, she did still win the vote totals and the amount of delegates needed to clinch the nomination.
If you brokered convention Biden (not even sure how this would happen) and replace him with a dark horse candidate like Clinton, Bloomberg, etc -- you're going to see the Democratic party go poof VERY quickly.
There is no way he is going to be the candidate. He can't go 5 minutes without spacing out, falling asleep, or saying something completely senseless. You think the leaders of the democrat party give a fuck about their image? Have you been watching the last 3 years? The Democrat party is already over, you just haven't figured it out yet. I would put money on either Michelle Obama or Killary taking his spot.
There's no way, in the modern era, to just replace the guy that just the majority of the popular vote and delegate vote in his respective party without inciting some sort of civil war within the party and causing it to fracture.
If he steps aside willingly -- ya know, by saying that he just isn't fit for the office and that the party should do something -- that's one thing. But forcing him out while he is out in the media disputing the claim, isn't going to work. It'll force the 'Obama Democrats' (the moderates) to turn against the party.
I know he's a horrible candidate and I agree with that, but I don't think they can kick him out without hurting themself more.