I'm working on a similar issue right now. I've had a midi pickup on a backup bass for a while going into a pitch to midi converter (I'm currently using the Yamaha G50). I recently started to play with my V-bass more and I am looking at a combined solution. Axon makes some of the best pitch to midi converters these days.
To use the V-bass at the same time (or just without re-patching) you'll need a GK splitter box. I think they still make a 1 in 2 out box, or if you're going off the wall try the 1 in 4 out

The previous poster is correct about the Midi aspects of the V-bass.
I am curious as to how well you like the tracking with your set up? What bass is the pickup on? I've had the older Roland and the Yamaha, and I just think I need a dedicated system (iGuitar or maybe the hex option on the Lightwave basses). Godin makes an acoustic fretless with a synth driver, but I haven't tried it yet. I might buy the Roland internal kit if I hear the new GK3 you're using is much better than the older ones.