If you want to do Drum Corps, then conform to the rules. IF you don't play the instrumentation that is current, then learn how.
I know many a clarinet player who play baritone because it doesn't affect their ability to play clarinet.
It's not hard. You know how to play clarinet, so that assumes you can 1. read music, 2. understand HOW to play music, 3. have a concept of learning and hard work.
Pick up a brass instrument, learn how to play it, then try out.
Why should our activity conform to you? You, if you're interested, need to conform to the rules of Drum Corps, or don't participate.
Pretty cut and dried, IMO.