Just a word on guitars going through a bass amp:
Bear in mind my first instrument was / probably always will be keyboards. We keyboardists used to plug into bass amps all the time before really good keyboard amps came out. A decent bass amp with a cab that has a horn tweeter will give you more high frequencies than you ever wanted.
I still would have the old school concerns about mic level vs. line level inputs, but now with the effects loop a keys player could skip the preamp entirely and go straight to the amp at line level if desired depending on what keys setup you have.
But as a guitarist, you don't have that issue. And there's a hell of a lot I don't know about guitar, starting with bar chords. But I would think that you could be very successful with a guitar going through a Rumble, especially if you were going for that fat humbucker sound like a Les paul or something similar. Even brights would work, though probably couldn't sound like a kid from LA with a telecaster and a California amp with no back.
Put it this way: If I still had my old Fender Rhodes electric piano I restored in the early 90s? I wouldn't hesitate to put it through a chorus pedal into a Fender Rumble. same with any of the newer Rhodes / Roland / Nord Hammond B3 modeling technologies. Same with pick-your-80s-horns and string sounds.
Point being, keyboards make noise on so many different frequencies, especially the old analog or digital analog stuff where you apply filters at various points below and above the fundamental. If keys do that, I don't see why a guitar wouldn't sound great through a Rumble. Especially the 200 or better which contain the compression horn.
I don't have keyboards gear anymore, but I'm pretty sure based on what I've heard the horn do with my bass, you could put anything from sweet Beethoven-ish strings to dance floor pounding horn hits through it. So while i'm pretty ignorant on things guitar, I'm pretty sure you could do well with anything from Les Paul to Stratocaster through it so long as the horn's on.
Back to bass, I'm absolutely loving the 15" speaker on my 200. I know everyone's using 10s now, hell even the sales guy at the place I got it mentioned a pair of tens in an extension cab to give it that extra punch. I'm afraid when I buy an extension, gonna be another 15".
Anyway sorry for the keys segue, but since keys players used to always use bass amps, I don't see why a guitar couldn't do so successfully. My thought being you'd want something with a horn in it like a 200 or better, to round out the very top frequencies.