Hey Marc...
The Roland GK line uses "Pitch-to-MIDI"... which scans 1/2 of a note's fundamental wave...
before converting it to MIDI. So... the lower the note you play... the longer the conversion time!
While this system sort of works for Guitar... it is just plain too slow to work for Electric Bass... especially 5-String Bass!
The delay time is just way too slow to play anything other than washy whole notes! My experience with it anyways!
However... Yes... there is an "alternative System"!
One that uses Fret-Wired Basses... with Piezo Saddle triggers... and an onboard Computer... that works just Great... and is Very Fast!
It's made by Australian Inventor Steve Chick. His new company is called: "Industrial Radio"...
http://www.industrialradio.com.au/
He formally Licensed his Technology to Peavey in the 90's for their Midibase & Cyberbass models...
but they discontinued those after only a few years?!?
I have the former Midibase model... and have used it on several Major Artist Shows & Sessions!
As a Controller... it "plays" my Minitaur just fine... and also can change Presets on any Synth using MIDI Patch Change commands.
btw: I also have IR's PRO-5 model on order as well now!
There's no perceptible delay... because it doesn't have to "figure out" what Note Frequency is being played...
while "waiting" to Trigger that note to produce a MIDI Note ON command for it!
IR's Basses are Fret Wired... so when you "finger" a note...
the onboard Computer "immediately knows" the MIDI Note Number right away...
then the MIDI Note ON command is generated by the plucked String's Piezo Saddle!
Here's IR's YouTube Demos page... where you can witness the Bassist "playing" various VST Synth sounds... in REAL TIME!!!
http://www.youtube.com/user/IndustrialRadioTV/videos
Their Basses are not cheap... but neither are any similar botique Company's Basses...
and they... don't have any MIDI Out available!
Best of Luck...
Cheers,
Briman