Would be neat to have PvP specific abilities (could only be obtained via Colosseum Points obtained by winning matches). They would only have an effect on players and could range from

Dirt toss (stupid name but meh)
Blurs the vision of your opponent
Literally makes the opponent's computer screen appear blurry so its hard to move and see what you are doing)

Disorienting Blow
Opponent loses his depth perception
Objects on screen may be larger than they appear (messes with the targets draw distance)

Confusion
Causes target to randomly select spells/abilities
You want to use Skewer II? Well game says you use Speed Surge instead!

etc etc