I remember my friend proposed doing this is red/blue in elementary school. I'm not sure if you're taking this into account, but you have to save before you trade stuff, and i'm sure before using the pokebank, so this would work as long as you don't mind starting your game over from scratch at the very end. It'd be much easier to go shiny hunting and trade those for legendaries
The only problem with storing all your Pokemon and starting over is that you cannot store items as well, so you lose event-only Mega Stones or items you may have obtained from the opposite version and such. Otherwise, yeah, it works.
YOU WANT SOME FUNERAL TO GO WITH THAT CAKE? | 3DS FC: 3437 - 4335 - 3104 | | Friend Safari: Panpour, Wartortle, Frogadier |
I have been doing this since gen 3, except I always used 2 systems and 2 games to trade to and from. I assure tou I have way more than 100 legendary pokemon, and I only kept the ones with nature that are not 100% useless, I realeased those a while back.