Regardless of your opinion, it’s not possible to put multiple instruments on a single line stave within a percussion kit - certainly not in the way you’re suggesting.
It might be possible to cheat it using Playing Techniques. If you need your three instruments (or any two of them) to ever play simultaneously, this proposed method is a non-starter.
You could try doing something along these lines:
- Add an Empty Percussion Kit.
- Add one instrument to it (Bass Drum, for the sake of argument).
- From the Single-line Instruments section of the Kit editor, go Edit Percussion Playing Techniques and assign two Playing Techniques (that you won’t use elsewhere) to Above and Below Staff Positions.
- Do whatever you need to do to explain to the human player what each staff position means.
For playback, I really don’t have time to go into serious detail today, but very vaguely:
- Go Play > Expression Maps. Choose Default in the left panel.
- Add the Techniques that you’ve used in the Percussion Kit, then tell them to do whatever’s needed to get them to play cymbal sounds. If you need to actually switch patches, a Program Change or some sort of Channel Change should work. If you switch the general patch for the Bass Drum to a mapped drum kit (from within the VST) then I guess just setting the playing technique to transpose might work.