Ahhh, a tinkerer by trade.
I see your point.
That's cool, yes you could always try another speaker in the cab as you said.
My recommendation is twofold: I wasn't sure if I'd like the 12, and stores don't stock the single cab, so i found one of the Rumble combos that had the 12 in it. I know all the heads sound about the same, so I was listening for the tone of the speaker. I was looking for a double-edge sound, but all-P-bass: I play a custom thing, what is mostly a P-Bass and emphasis on killer P-bass tone; the tone I like is something like Dave Hope's (Kansas) throatiness, and Mars Cowling's (Pat Travers) punch and pop. This cab has that. It also has a lot of super-tweety high end which can be tamed with the 3-position switch on the back.
To me, I think the 12s sound a lot like a good old-school 15, not so much woompf but a heck of a lot of midrange bark, which is what I like about 15's. After the 80's and 90's, I am the antithesis of the scooped sound. The 12's might be able to get it, but don't bother me with those shenanigans...Actually, I think the scooped sound has become old school, certainly overdone. But I digress...
Another option if you aren't sure if you like it is to buy one, delivery as close to a gig date as possible, if you don't like it return it.
When it arrives, The first thing that will strike you is how small it is, and because of that what a terrible mistake you have made. The next thing is how good it sounds. At a gig you will wonder how something so small can get the job done. Then you will look at it, and realize how cute it is. At least that's how it was for me.