Speaking to tvguide.com he explained: "You know, if I get a chance to use Allyson, I'll use Allyson. That's a given. There's no maybe about that. The maybe is, does she have time?"
He also stated that he has been in touch with Alexis Denisof (Angel's Wesley) over the matter but again nothing material has come of it. Also, he confirmed that Amy Acker (Illyria) is interested in the endeavour.
As for where the the project stands, Whedon explained that it is very much in the planning stage. "We don't have a paradigm set up yet. We don't have anything solid to announce," he explained. "I'm just making sure that the creative people I need are in place before I set up a whole deal and then James Marsters (Spike) goes, "Gosh, you know? That's kind of behind me now."
"Or [if] I don't have a writer I can trust, because I don't have time to do it all myself; I need one of my peeps. And there's no greater peep for something like this than Mr. [Tim] Minear. I'm optimistic that I will actually have something to say in the near future, but at this point it's still me and my buddies going, "Wouldn't it be cool?"