In my opinion a good "fullrange" driver can do many things well, but the frequency extremes are generally not among them. I'd be inclined to keep bass frequencies out of it and use a dedicated woofer, and to add a tweeter to improve the top-end dispersion (and extension if needed).
There's a speaker company in New York that does this. I think their name is Bache Audio, or something like that.
;^)
My first commercial effort fifteen years ago was almost that (6" Fostex + powered bass section + tweeter), but I made the fatal mistake of not high-pass-filtering the "fullrange" driver. Might give it another go some day.
The best single-driver, truly fullrange speakers I've heard are the big SoundLab electrostats.
Duke
disclaimer: I'm a SoundLab dealer