I think the current Organteq model already does #2.

Interesting indeed. I'll try to check this...
-Michael

1) Note-on and Note-off velocity.
I found reports from Pipe Organ players that prefer a completely mechanical organ design over an electrical one, as they want to be able to modulate the tone by moving the keys slowly. My VPC 1 keyboard generates Note-on and Note-off velocity and I understand that the physical model should be able to cope with modulated rising a falling slopes of the wind pressure at the beginning and end of the tone. I suppose this will make a lot professional organ players happy (and would be hard to do with an instrument design based on samples).

2) Intermodulation
To me it's obvious that a high pitched pipe will be modulated by the air pressure fluctutions introduced by low pitched pipes playing nearby. I 'm sure that the physical model of the pipe should be able to reproduce this behavior (while it's impossible with samples). I suppose this will improve the realism of the instrument.

3) User generated stops
It should be possible to allow the user to create additional transposed stops and fine-tune them (e.g. to natural overtones) to get 5th, 7th, 11th, 13th harmonics that are not yet provided at all, and to create any harmonics playing in dedicated sounds and possible (de-) tunings.

4) Free Mixture stops
It should be possible to allow the user to create mixture stops of any available Pipes (e.g. see "3").

-Michael