Mightyena Was Caught?

I know I've drawn a ton of Mightyena since discovering Pokemon Ruby/Sapphire. Funny because I initially HATED the games to rejecting the creatures I'd amassed in Pokemon Silver. At any rate, a random female trainer's bagged herself a lifelong partner, and he seems to recognize her prowess as a trainer right away.

Why can't Mightyena have an awesome Mega evolution to look like this? Pokemon needs something like what Digimon has in Weregarurumon.