If you look deeply enough on the GTS you can normally find some good stuff for non legendaries, and if you are searching for a specific pokemon, you can always turn off the special pokemon option, and it removes most of the pokemon that will only trade for legendaries.
Most of the reason that only Kalos native pokemon are allowed in the torneys is because it almost garentees that the pokemon arent hacked or otherwise cheated into the game, as so far there is no real way to get pokemon generated on your comp onto your legit or downloaded X and Y save file because of the games code.
Those who have managed to get hacked pokemon through pokebank, of which there are a scarce few, if any at all, can still of course breed their perfect pokemon so that they become Kalos native, but that will be a rarer occurance then in previous games where it was fairly easy to get around the data management for games on the DS and GBA.
Ive got a few of the rarer pokemon that have come through the bank if people want them as well, so send me a message (pokemon like tynamo and lileep)
Also I havent been posting here because I'm rarely active on the site and this thread died a while back anyway before people were posting again.