So we cannot define a bass trombone simply as something that can play low E♭, nor low B (only a straight tenor is incapable of this). I think it is silly to try and create a black-and-white distinction between tenor and bass. On the contrary I think we should preserve all the shades of grey in between, as a painter uses every shade of a colour. We should beware of making hasty judgements on instruments described as “special” (the ear has difficulty in accepting sounds it is not used to). Let us be objective and just think about the music.
In conclusion, let us hope that trombones preserve their range and variety and are not further reduced in the name of some simplification incompatible with art. And we bass trombonists should take advantage of our specialised knowledge to adapt our equipment to the music we play, maintaining a balance between the parts. Let us also appeal to tuba players to take an interest in the valve bass trombone and also to the double-slide contrabass trombone, which seem to be intended for them.
P.S. I would be happy to correspond on this subject.