This sounds like one question but really it's three:
- Does it have to be about physical fighting or can it be any type of skill-based competition?
- Does it have to be set in a fantasy world or can it be grounded in reality?
- Do the characters need to have superpowers or can they be ordinary people?
Basically I've been thinking more in terms of Bakuman (a Shonen which some would argue is "battle manga"), but I'm willing to go into a more Dragon Ball/Naruto route if it would fit the theme of the jam better.