Currently the only case/bag I have for my euphonium is my Altieri gig bag, which I love. I think it meets all of your criteria with flying colors... except for maybe protection. I have had no issues with small bumps getting it around the house, on trains, and around town on the rare occasions I have taken it out and about in Chicago, or getting to rehearsals and performances in my own car. But anything beyond that... well it is just a padded bag.
I have no first hand experience with the MB cases but it certainly seems that it gets the closest to everything you could ask for in most settings.
Does anyone have any first hand knowledge of how the JP Pro bag compares to the Bonna?
I will also add that when David Shinn shipped my New Standard to me it came in a wooden case that seemed well built and sturdy, although heavy. That case ended up moving on with my Schiller when it found a new home, but for the brief while that I had it I enjoyed it. Of course it was heavy, and had it left the house I might not have enjoyed it as much as I did in the corner of a closet.