Resurrecting Topher would be a BAD idea for Whedon to kick off his run. Despite his namepower (which will at least double sales, at least for his first issue), Whedon will have to appease the small-but-loyal RUNAWAYS audience (usually about 22,000-24,000 readers) that he has the goods to continue after Vaughan. Resurrecting Topher the Vampire would pretty much be Whedon saying, "I am a hack who, like Bendis and Claremont, have no more original ideas left and all I can do is rip off and strip mine my past material, over and over, until I am dead." Considering Kitty Pryde is essentially Buffy with phasing powers in ASTONISHING, one could attempt to say that now, but that would be short-sighted and untrue. But if he brings in a vampire, any vampire, into this book, he will have that "hack" stink on him, and that would be sad. It would be like Claremont doing YET another Shi'ar story, or yet another "Storm gets captured by someone who wants to make her their queen" story, or so on.
Besides, Kristoff Vernard is there just BEGGING for a decent writer if Whedon wants another teenage male on the team (presuming Chase bites it in BKV's finale).
So, no more Topher for me. He was a decent one-shot villian, let's keep him that way. He wouldn't work as a dopey resurrected anti-hero, and Whedon would be the wrong man to sell it.