Interesting, as that’s obviously not a typical pickup layout. IIRC the necks on these are quite chunky. All of which makes a new build/purchase a potential stab in the dark. If you wanted to go for just one bass, based on your current preference, a Billy Sheehan Attitude would be a good way forward. However, a brand new, current release, looks spitefully expensive, which means used may be the only option if you wanted to keep the BS vibe & feel (you may have a huge budget of course). Another way forward could be to keep the 714BS and also have a P/MM layout bass (as I think you mentioned) as a contrasting alternative, although the necks might be quite different.