How about a Brinstar-type mod (the stage from super smash bros. melee and brawl) where both players are on separate platforms? The platforms' closest points are about 20 cm from each other and there is lava below the platforms slowly rising it's like 25 cm from the bottoms of the platforms but rises at a medium pace/slow pace and tori and uke must jump to stay alive and dominate the skies to win? Of course it'd be also good to tweak the gravity to see what suits this mod best: do you reduce it and let fierce air battle determine who stays alive, or increase it and make tori and uke really work hard to stay on top?