I know the problem you have very well. I tried for a solution to the problem with my Bach LT16M slide bone combined with a V16 valve section. I had a hook on my music stand for both the valve and slide sections when not in use.
In the end I found it too time consuming and awkward to try and switch the valve and slide sections around whilst playing on stage. So, I got myself another bell and used two trombone stands.
Guess who I got the extra bell from? DJ of course!
Of course, it did mean I had to carry two trombone cases.