Not sure if you still need this, but here goes.
Take
Hindenburg the Drifloon/Drifblim.
Like its irl counterpart, Hindenburg was filled with hydrogen instead of helium. As such you're extremely fearful of fire, and must switch out and stay out for the rest of the battle (That is, unless Hindenburg is the last pokemon left) Since Hindenburg is also a balloon/blimp, he is easily blown away by flying-type pokemon and must switch out, like fire-type moves. You must continue doing this until level 50 (or when Hindenburg learns explosion through a different method), when Hindenburg obtains enough Hydrogen to learn explosion and evolve. Once it evolves, whenever it gets hit by a fire-type move it must explode like the actual blimp. (You may use revives to bring it back however, unlike drifloon) Hindenburg must also have the ability aftermath and the move Payback, so it may always have the last laugh.
(Tell me if this isn't hard enough or needs more challenges, or if anything needs explaining.)
EDIT: You may switch Hindenburg back in when hit by a flying type move because it isn't destroyed, just blown away.