So you don't want to play bass solos as such, you want to be a solo bass player.
I'm not much into that, although it's an interesting thought. I think the guys like Michael Manring who specialize in that style are intimately familiar with alternate tunings. Manring has a specially designed bass that he uses to change the tuning of each string on the fly. I don't think you need all that yet, but it may be worth checking out, just to get a listen.
There is a guy here that wrote a book on playing solo bass. Think his name was Mike, so you may want to search around for that also.