QSC builds powered speakers perfectly capable of working as beautiful bass amps now.
In fact they are part of many FOH systems that amplify the bass to levels the audience hears.
Taking out the horn for a bass only model, would probably cost more in retooling than just build a general purpose cab like they do now.
Go give them a try, I'll bet you'll be surprised if you don't think they can do this now.
PS - if QSC decided to make Bass only amps, then they'd have to go about publishing little or misleading measurements and specs. I don't think their ready to go this route.
