You don't want to just have a set of capacitors, that's like having the tone rolled all the way off all the time. The cap sets the corner frequency, not the amount of roll off. You would need to experiment with resistors in series with the cap to figure out what combination makes a worthwhile pre-set.
Yah, if I were doing it I'd have a trimpot for each capacitor, dial in the amount of rolloff for each position and then close it up.
Myself, I need an adjustable tone control. So I'd have three knobs. Volume, tone, plus a rotary for a couple of different caps.
If accidental nudges were a real problem, the rotary could be located between the volume & tone knobs.
On most basses, though, there's enough space that I don't think I've ever turned the tone knob by mistake.
If I were doing it, I'd use a PJ bass pickguard - it has holes for three knobs - and put the output jack on the side like a PJ, too.
Like a PJ without the bridge pickup. Of course if it were me, I'd rather have the bridge pickup than a cap selector.
~
One of my HSS superStrats came with two knobs and three mini switches in place of the center knob.
I replaced the tone control with a dual-concentric: one for the bridge and another for the middle & neck.
Wired one of the mini switches (DPDT center-off) to select two different pairs of tone caps or tone bypass.
Seemed like a cool idea at the time, but turned out to be a needless complication - I hardly ever use the other pair of caps.
I do bypass the tone circuit occasionally, for a little extra sparkle. But IMO it wasn't really worth the complication.
Also, dual concentrics aren't at all ergonomic on the fly. I knew that but chose to ignore the fact.
I rationalize the project as a sort of test bed - experimenting, a learning experience.
Looking back over the decades, virtually every time I've wired more complex capabilities it wound up not being worth the time & trouble.
Pull-to-split is handy on humbucker axes, and autosplit is handy on Strat types. For me, nothing much beyond that has really been worth it.
I could see maybe trying spin-a-split someday though, if I ever have a guitar with an extra unused knob.
