While I agree that making a Buffy movie without Joss would almost certainly result in a different interpretation of both the character and the way that she is presented, I can't say at this moment that the end product is going to be necessarily bad simply because of that difference. I realize that all of the old cast and crew, or at least the ones who have voiced an opinion on the subject, have been basically unanimous in their support of Joss and his retaining creative control of his character, it seems to me that that is really all that it is: loyalty to Joss. That's certainly commendable, but he isn't the only writer or director in the business, or even, blasphemous as it may sound when I say it, the best. He assembled a group of actors to portray a group of characters who touched someplace very special in each and every one of our hearts. That is a fact that I don't think that anyone here would care to deny, any more than we would deny that there can never be another Buffy like Sarah, Giles like Tony, Spike like James, and so on. But since apparently none of those characters are going to be portrayed in the proposed movie, even Buffy, since this is supposed to be a total reboot, none of "our" characters are under any threat whatsoever.
I intend to see the movie and let it stand or fall on its own merits. I may end up hissing at the screen and throwing popcorn just like I did at Jeff Bridges' Rooster Cogburn, but I'm gonna at least give it a fair shot at entertaining me before I do.