That's the whole problem with the coup.  If there's a potential leader to be found on short notice within the pool of Labour MPs, it's not obvious.  Everybody's locked into either the Blairite or the anti-Blairite factions.  Nobody's really got a vision for what Labour should be.

Simply saying "Recruit a bunch of young progressives to run against establishment figures" sounds great.  In the US, you can do that via our primary process and grassroots fundraising.  Dem and Rep activists have both pulled it off in recent history.  Not so easy in Britain.  The parties there are incredibly powerful.

Be nice to America. Or we'll bring democracy to your country.