I have something much different in mind but am not so interested in making it a community event as the most important thing for me is how an instrument creates the palette of colors that I want. Very few people work at this level.
Many of the things you are thinking about I have experimented with and will flow into my efforts. The only thing left for me to finalize is the ceramic rotary valve block. I am currently using carbon fiber for the rotary valve innards.
A crystal glass bell would be best blown not milled in my opinion. Even your bell shape would be possible in one piece. Watching a good glass blower is a great experience in how breath support can be used in very much unrelated ways to our playing.