James, when I get my MS back, I will do some work on setting up a style using GIGA souns/VST's.
Also you should not really use the term GM bank , as that just makes unenlightened folk assume " dodgy GM sounds"
They do not realise on the MS the user can CREATE their own GM bank.
All it does is use the GM numbering system..0-127 not the dodgy GM sounds!!
The first ten patch slots can be 10 guitars if you want, followed by 20 basses, and all of these can be a VST OR giga patch.
Then you assign your patches to either the style or the sequence by editing and saving...
If a user wants they can follow the GM patch numbering and naming order in having pianos, EP's, chormatic percusion, organs, guitars, basses etc, which I guess then gives the advantage of ANY GM midi file working on the MS OOTB.
But with killer giga an vst sounds instead.
Anyhoo, I will attempt to get something in a style demo done. Hopefully taking some of the pressure off you

Dennis