There are a number of options. The highest output humbucker-size Q-Tuners are the GL Super High-Z. They also do Medium-Z, and High-Z.
Sustain is apparently great. They are also noisless. Only thing they
aren't, is "vintage", and this is where people will be put off somewhat. As I said, what's needed is some sound clips, preferably done by someone who's playing we are familiar with. Cause if
Steve Vai was rocking these, you bet they'd sell, right?
I think they're probably amazing. I just can't afford to take the risk in case they are not!