I'm curious, are you being offered an "either/or" scenario? What is the audition/placement process like with your line?
In every line I've ever played in or taught the members earn the spot they desire by showing that they are a greater asset to the line on the instrument of their choice than the next person.
IMO you should take the bass spot and bust your butt to make that bass line the best in the state/circuit/world and work up your quad chops outside of rehearsal for next season. This will also prove to the staff that you're willing to do what is best for the line as a whole.
- Worst case scenario: you're bass section leader again next year (Senior year) and can be part of one of the best bass lines in the state/circuit/world and can try out for quads at an indy, DCA, DCI, or college line.
- Best case scenario: you
earn a quad spot with your hard work.
see
this for some more insight into what (most) staff members look for when setting the line