Quark, you still reserving, otherwise I"d like to give celever a mon.
@CrappyGyarados, seeing as you haven't gotten many reactions to your post, take Nuts the Seedot. Seedot will be your trusty warrior throughout the game, but it realizes it is a really small seed. Therefore, to gain confidence, it has to use Growth at the start of every battle, until it has OHKO'd 20 trainer owned pokemon, after which it can evolve. As a Nuzleaf however, Nuts finds himself falling prey to overconfidence. as a result, you restrict him to doing exactly what you say. You teach him to only use nature power as his sole attack as a nuzleaf, to admit a strong warrior always pays attention to his surroundings. Nuts can evolve again afte solo'ing the Flying type gym, because it realizes it did something praiseworthy and is ready for much more. As a Shiftry, it wants to expand on its movepool, and learn moves of 4 different types ASAP, to be sure he can hit a lot of pokemon super effectively. Shiftry has one downside though, whenever it fails to OHKO a traienr owned pokemon with a super effective attack, the attack it uses on the next trainer owned pokemon can never be super effective.
GL
@DragonBreath, take Grassss the Treecko. Grassss is a huge fan of battling with its gras typing, so it has the wish the purify itself. To purify itself, it has to absorb grass from 10 trainer owned grass types by using only absorb / mega drain / giga drain against them. Upon doing this, he has absorbed so much grassyness that it is fond of himself and can evolve once. Consequences are however that he gets afraid of touching the opponent, as they would make him all unclean again, so Grassss does not want to touch opponents ever again. (no physical attacks) If he does however, he has to purif himself again by solo'ing 5 grass types (wild or trainer owned) with absorb / mega drain / giga drain before he can continue battling. After solo'ing two gyms, Grassss can evolve a second time and realizes he is faaaaast. However, whenever Grassss gets outsped in his final form, he gets depressed and throws away 10 items of your bag (not a big deal, you won't have enough room for all items anyway). He really wants to solo the ice type elite four Glacia to prove his worth to you, as his final test.
GL