I need some advice: I've been asked to consult on a ground-up swiss army knife approach to a powered speaker that could function in multiple roles, those mostly being PA, guitar and bass. Now, it's my opinion that those are three different animals, but modern signal processing has gotten way better in the last couple of decades, and it might be possible to build something that's pretty useful in live situations. To some degree it is already being done, so question (a) would be for feedback on which brands/models are the "best" of these amps. Cost is not necessarily a major concern there.
Question (b): it seems highly unlikely that anything but a very specific few amps could be built in and controlled via traditional knobs and switches; say, PA, Ampeg B15 bass amp, and Marshall JCM 800 guitar amp. That would be very limiting. My mind rapidly goes to something that is at the very least controlled through a touch screen, and even more likely, controlled via an external controller (iPad, etc.). I've seen the latter done for PA rigs that are actually mixed in the operator's hands, and it didn't seem to be an ergonomic nightmare. Of course, don't lose the controller. Do THESE options exist for guitar and bass rigs? Would it bother you guitar/bass players to have to dial in your amp choice, change settings (volume, gain, EQ, reverb, etc.) this way? Is it unreasonable in a live setting?
I don't want to get into the reasons why this product might be differentiated from what's already out there. Suffice it to say, there would be differences.