I believe you can get very realistic bass parts in midi with the use of very good sound sources and midi controllers. Note that the use of very good sound sources also means more money than a simple GM set.

However I do not believe it is possible within BiaB for two reasons. One is the one midi out port; yes I know there are work-arounds however BiaB should have more than one midi out port-period. Secondly and more important is the fact that the midi resolution of 120 PPQ is to course to allow very fine midi control. With a midi resolution up to 960 PPQ one can get a more realistic live playing character and the triplets that dpresley mentions. All sequencers that I know of can be set to at least to 960 PPQ and that includes RB. So one would have to create and/or modify their bass parts in a sequencer to achieve better sounding midi bass. IMHO this is also true for any midi instrument.

Just my two cents.

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware