Cooper and Starmer would just attract negative press about their Blair connections
I honestly don't think they would - not to the extent that JC does by a long, long way. And unlike JC, esp in the case of YC, there are many good things that have been done that could be pointed to in rebuttal.
I know Blair will be forever tainted by Iraq, but no one hates him as much as his own party do, and that's ridiculous because he was immensely successful. The failure of the party to celebrate that is one of the reasons it's in the shit it's in now and JC is a big part of that, pompously refusing to share a platform with Blair and arrogantly (and ineffectually it turns out) talking about having him tried as a war criminal. I'd also put some blame at Ed Milliband's door as well, as in the early years of the coalition there was too much passive acceptance of the ridiculous notion that Labour had wrecked the economy and not enough talking up of the good things that had been achieved. At that's all at Labour's own door.
As for YC and KS, what could they be accused of? They're not accused of colluding with Blair/Bush etc are they? So they voted for the Iraq war? Going on information they were given, the same as all the Tories who also voted for it.
Jess Philips?? FFS. This suicidal idea that we can't have a competent and experienced leader because they have worked with the most successful leader we have ever had has got to stop. It's killing the party and, more importantly, allowing the Tories to damage, perhaps irreparably, the welfare state, harming the most vulnerable people in our society.