I wish he could figure out what he wants, or learn to accept the subtle little things and just choose to be happy with a bass or two. I guess I just don't have the ear for all the subtleties that he hears. Mostly a Roscoe sounds like a Roscoe to me, with some variations. I can't be too hard on him. Years ago I went through basses like crazy. Sold some while they were in shipment.
A lot has changed for me since then. I have my Koa Century 5 that I will probably always have. Not my first Roscoe, but my favorite. I'm not playing it much these days as my needs and bands have changed a little. I find the "P with flats" thing is working these days. Thankfully, my wife bought me that Roscoe Classic P for Christmas last year. It has become my main/favorite bass. I would have never thought that anything would knock the Koa 5 out of that spot. If I were still playing contemporary jazz, fusion, that kind of thing, it'd be the Koa 5 no question.
I also have a Fender 5 string P (with rounds) that I use when I want that P sound but need a couple low notes. I really only need it for a couple songs in the cover band. I have actually thought about using my synth for those tunes (Uptown Funk and Pour Some Sugar On Me) and just using my 4, but it's kind of fun to have a couple basses, for variety and backup I guess.
Passive 4 string P bass, REDDI tube DI, that's my sound these days. Very different from even 10 years ago.