Some of what you say makes sense, but I'm still calling shenanagins on this post. Now mind you, I'm not a tuba player, but would someone care to tell me how writing tuba parts in treble clef is a good idea at all. Seriously.
Also, correct me if I'm wrong, but since all brass instruments are built based on the overtone series, this gets rid of the need to learn an entirely new set of fingerings for different horns. C is open on a Bb, Eb, F, G, or C trumpet. So what is the issue? Again, I'm not a tuba player and I don't feel like opening up an orchestration book right now. Explain my good man.