@Oscar Stern, as someone who also has some personal obsessions with the double bass and with other instruments, I can understand how a pet idea that is different doesn't get a lot of acceptance and that it can be frustrating. But, if it's important enough to the person developing a project based on such an obsession, that person has to prove it as truly being useful, better than whatever the standard is, and really worthy of acceptance...
This is just one of many threads you've posted in, talking about the same thing with a few different leans. You're talking about your ideas to a large group of people who are using what would be considered the standard. Many of these people are very highly educated, have decades of professional double bass experience and are fluent at producing beautiful music with their standard double basses.
Talking is not enough. Theory, specifications and design are also not enough. Debate will not convince anyone. And no one else is going to prove it for you. If you want people to believe in your concept, you will have to demonstrate it in real life yourself, and that demonstration will have to include the ability for side-by-side comparisons of quality instruments.
I doubt that any serious double bass player has any doubts about double basses being hulking large instruments, difficult to transport, and always somehow in the way. That is in your favor. But until you produce a prototype demonstrating your concepts, you aren't going to convince anyone.
I would suggest, and would actually challenge you, to take a break on just talking about this and work on some prototypes that eventually can be used to demonstrate what you think. Your prototype will need to be fretless, bow-able, will need to be pizz-able and maybe slap-able, it will need to be functionally able to be played standing or sitting, played just as a double bass can be played, so that someone who is a professional double bass player can step in and play your prototype without having to change techniques or postures in order to accommodate any differences. And it will need to sound acoustically and amplified the same, in the same note ranges, as a standard double bass.
If you are successful, it will be something that people have tried to do, unsuccessfully, for about 450 years.
I wish you good luck with this!