After some more trial & error:
1. Add a Guitar Pro Mapping Preset. Or allow Users to upload & share their Mapping Presets for Keyboards, Software, etc.
2. Allow multiple keys to hit the same midi sound.
3. Add a "follow Bandmate" option like EzDrummer, Garage Band, Logic and several others offer. This would be highly needed for Modo Drums
4. Ghost notes are a pain in the ass. Add either keyswitches, aftertouch or cc for ghost notes. Would make life and Modo Drum much easier.
5. It would be great, if you could add some odd grooves in 7/8, 13/8, 5/4. Or allow users to add their own grooves and time signatures.
6. The cymbals in Modo Drum don't sound realistic although everything else sounds really good. Add sample based cymbal libraries to Modo Drum. So everything will sound realistic.
7. Micing the kits and customizing the mic positions is highly needed.
8. Also it would be really great, if you could add a TR-808 or TR-909. Roland already offers plugins but those are really bad and too expensive for what they offer. Even some freeware is better than the Roland ones. Maybe you could offer it as an additional sound, like the Brit Custom or Metal kits.
9. Percussions would be great as well. Bongos, Congas, Cajon, Maracas or even an indian Tabla would be highly welcomed. Or maybe a release of Modo Percussions? This would be a huge help.