Wario bike parts confirmed, though not too far. Toon Links Bombs also confirmed.
If Wario's bike parts can work, and he's a heavy character, then I think it has to do with frame timing rather than only light characters and for some reason Wario can do this. You should also test this with every character just because it's something you can use in battles against these item casters, especially since it's so much easier to catch items now.
Something else I want tested by anybody, Wario Waft (the fart attack) is extremely good for recovery, but it takes time to charge. I figure the one thing that could charge it faster is his bite attack. So, I want tested:
A.) How long does Wario normally take to fully charge the Wario Waft? He starts flashing/slowing when it's fully charged, so you can tell. You'll need to test from when Wario respawns and for when Wario uses the move and goes back to empty (I think he has part of it charged whenever he dies)
B.) Does Biting other people speed up the charge?
C.) Does Biting (and eating) items speed up the charge? Wario has his bike, so he always has something that he can create and eat if necessary, and would by extension be a great boost to his recovery.