Maybe there could be certain effects you could buy? Like water-breathing, zero fall damage, grasswalk (turns dirt into grass when you walk on it), +1 block to jump height, Extra lives (if you would die, you lose the extra life and get restored to full health), Invisibility (except for the name, of course), etc.
Of course, all under a certain amount of time. Like, you'd buy X minutes of (effects) for Y # of voter points.
Sure, they're functional, and give a slight advantage, but as Dukem said, anyone and everyone can vote, so it's not like it's an 'unfair' advantage. Plus, they're only temporary effects for what would likely be a pretty steep price, so it's not something that I could see being abused.
Just a few ideas to throw into the mix, while we're still talking about it.