Funnily enough, I like Battling in MKWii more than Versus. I know it's weird, but can we?
The way I see it, the speedrun wouldn't be to win. Your goal would be to reach a certain number of points. One idea I had was "Collect 100 Coins". The timer starts as soon as you enter a stage in Coin Runners. The timer ends the moment your point total + the number of coins you currently have during the battle sums up to 100. For example, if I had a total of 90 points in between stages, the speedrun ends as soon as I collect the 10th coin on the next stage.
For Balloon Battle, why not emphasize your love for popping balloons by getting rid of yours as soon as possible? Sure you could watch things get slowly destroyed in a fire, but why not settle for the gratifying instant destruction of a balloon? One moment, it's there. Then suddenly - POP! - gone for good.
