Vquestor, I might not be understanding you correctly but sYnerGiGS plays GS, GM and XG midi files and styles as well as any other software wavetable available today. I have contacted Darrell Marjoram on when he plans to complete the full XG wavetable. He has given no indication, however, 23% of people frequenting his site and voting are in favour of this as his next project. It is the highest on his list.
The problem is more in the other direction, i.e., using other Wavetables (Hyper Canvas) to play Yamaha styles or midi files. Yes you can take and transfer the sYnerGiGS drums to other soundfont wavetables using Alive and you are in business with different sounding wavetable. I have done that with the following:
Ntonyx
Akai
Fluid
GeneVoice
JurgenGM
MerlinGM
Personal Copy
Sonic Implants
Sound Canvas (soundfont version)
SonicReality
Utopia
Xiod
What do I use? Well, sYnerGiGS modified with better accoustic instruments, e.g., pianos, strings, guitars, brass, etc.
Now Vquestor if you mean someone should attempt to sample Yamaha's keyboards - well some of its being done but it is not so easy. The following is an example:
http://www22.brinkster.com/guraydere/ Sampling is an art and science unto itself and would not want to attempt this in the twilight of life - how sad!!! Given that most of todays top of the line keyboards have at best medicore to moderate quality acoustic instruments sounds, you would be into looping, layering, LFOs, etc. to make them sound acceptable. This is to hard for an old man. This is, of course, true for drums as well.
You could as you have suggested use the sYnerGiGS Drums/LiveSynth Pro with other wavetables, e.g., Hyper Canvas (drums turned off). The sYnerGiGS Drums are of moderate quality - not quite as good as some others.
Now for the Live - Styler crashes I have no answers other than not giving up to soon. I had them initially but eventually did the right things on my system for it to work properly. Mine was more to do with midi port/channel assignments. Have you tried the factory reset? Did you do a full install? Sometimes some of the initializing files are missing or corrupt.