We have an odd situation whereby the orchestra has never gone to the trouble to permanently replace a second trombonist - as there are quite a few talented players in the area who all do a nice job of playing with the section. I sort of have a deal whereby - if there are no tuba parts on a concert, yet there are three trombone parts, the bass trombonist moves over to second, and I cover third.

The last time I did this, I covered the bass trombone part on Schubert 9, and it worked out fine - if I do say so myself (last movement is on YouTube, if anyone's curious)...
well... okay...Just last month, I covered the bass trombone book with the F cimbasso on a big-band-with-strings pops concert.
As can be found in the repairs forum, I'm in the process of building a B-flat (regular bass trombone length) trombone cimbasso (with both a playing slide and a two plus four configuration valve section), but the completion of this project keeps getting pushed back for customer repairs.