This somewhat describes my history. If I had known about drum & bugle corps when they we 'fitting' us for instruments in 6th grade, I probably would have taken up trumpet instead of saxophone.
What would I have done in your scenario above? I would have auditioned for a lower tier or open class corps, learned a brass instrument, and tried for my 'dream corps' the following year.
To me the brass sound with froward projection is what makes drum & bugle corps distinct from other marching activities.
There will always be things that don't work out because of decisions and circumstances earlier in life.