Mismatched knobs?

Go for it. If you don’t like it, it’s a very reversible modification.

 

Maybe Accessories, but I believe knobs are Hardware.

 

I don''t see an issue with it--it may bother some OCD people, but it's your bass, not theirs.

All mine match--but I have replaced some for different types.
And I have a guitar with a "Tone" knob on the volume pot & a "Volume" knob on the Tone pot--but that happened by accident--and when I saw it--I left it.

 

When I bought my son his first Stratoid when he was about 10 or 11, he also wanted different knobs. So one of the first mods we did was to go to a hardware store and look at all the kinds of knobs available (when you could still do that sort of thing - I think we went to Radio Shack). I told him and showed him of the selection which ones would fit and why, and which ones wouldn't and why. He chose a few to try and swap around. A great time was had by all.

 

I forgot to mention to the OP: you are in good company. John Lennon changed the treble pickup knob on at least a couple of his guitars so he would know which one was which, as many of the electric guitars he played, at least on stage, were Rickenbacker and later Epiphone, with four knobs each.