One problem with using a super-tweeter is it throws constant-directivity out the window. There is no way to crossover to a super-tweeter without interference notches at narrow vertical angles near the forward axis. The distances are too large and the wavelengths too short. So what you get is a speaker that is only right straight-on axis, and any movement causes all sorts of response anomalies. I'm not sure that's a compromise I would make.