Game Freak often do event giveaways of Pokemon with special moves. What if they did the same thing, but with abilities? I.E. a Pikachu with an ability it couldn’t normally get (say Adaptability, for example) that it couldn’t pass on by breeding? I think this would make the games even more interesting, and be another way of giving older Pokemon access to newer abilities.
Eh… to be honest I’ve never really been fond of event-exclusive Pokémon; it annoys me when companies put things in their games that you can’t get by playing the game. I don’t quite see what those things add.