FWIW, a friend of mine did something similar to this in a mead. I don't know if he let it ferment w/ sacc first, or if he just let the kombucha do all the work. As I recall, the mead turned out OK, but without much sour/kombucha character. It wasn't bad, but it wasn't that great IMO. It just kinda tasted like mead to me. It was over a year ago when I tried it, though, so I don't really remember.