I think I have to agree with those that say BtVS shouldn't be remade. While there are aspects of the show I think could've been handled better, for the most part, I love it as-is and don't want to see anyone try to remake it. My biggest issue with remakes is that, most of the time, they end up failing because everyone compares it to what came before, or, it just flops because those in charge didn't understand what made the film or show great in the first place.
That being said, I would be totally okay with a spin-off or any other additional BtVS content I could get my hands on. Honestly, if they're going to make another BtVS show or film, I think they should go animated, and maybe air it as adult swim? I'm not sure if BtVS and the adult swim audience would typically mix, but I think it could be cool...maybe that's just me.