I've been fooling around with two different synth hardware pieces: the Yamaha Motif-Rack XS, and a Moog Sirin.
I can control everything in the Motif from the bass, and it provides a larger variety of instrument and non-instrument sounds. And I can isolate to synth only, mix-synth with bass, or bass only, and select sound patches, all controlled from the bass.
I can trigger sounds from the Moog Sirin, but I cannot control the sounds (e.g., volume of the Moog; or isolating synth and bass -right now it is synth and bass all the time). So, I'm not sure yet how usable the Moog triggered from the bass would be live, but it will be fun to use it on tracks when recording. It is still cool to be able to trigger the Moog from the bass and modify sounds with all the Moog settings, so hopefully I'll be able to figure out how to isolate the Moog and bass and control the Moog volume for live use. Those analog synth sounds are pretty cool. I will explore signal splitters and foot switches and see what I come up with.
Steep learning curve for all of this, which takes time in this busy world.
Fun stuff though!