Jimera, Take Healfodder the Karrablast, as early as you want him.
My obligatory long backstory is in the first spoiler tags, the restrictions in the second.
God I must stop making these overly long stories, they are a pain to write and a pain to read.
Take a Karrablast. This Karrablast has been a hermit ever since he got back from his adventures with Waterwarrior, due to everyone who met him only remembered him as Healfodder. Out of pity, you catch him, but your trek through the game proves he still can't use physical moves. He still tries to help you though, retaking his old habit of switching in to die whenever anyone needs healing This all changes, however, when he is submitted to the electrical field of Chargestone cave. As soon as he enters the cave, a strange power knocks him out until the end of the cave. When he comes to, he starts babbling about having a vision. Long story short, he is a descendent of a long line of thieves, and his lack of physical power is due to him not withholding his families ways. He also mentions that due to a cut, he hears the beginning and end of a prophecy, mentioning him stealing a shell, and power greater than Arceus. Basically, due to him not knowing thief, a weird thing considering he comes from a line of thieves, you have to fake this by using an item on him that a trainer has used against you in battle. Every time you do this, you gain access to 20BP worth of physical moves, meaning after 2 "Steals", you get to use 40BP physical moves, 3 gets you 60BP and so on. Finally, when you hit 100BP he learns that the shell of a Shelmet grants its owner unlimited power. Of course, he believes that this is the shell the prophecy speaks of, so of course, you can evolve him after fighting a Shelmet. One issue though. After he evolves, he learns the true nature of the prophecy. The Shelmet he stole from is the decendent of the Mighty Warlock Accelgor, who cursed the Escavalier line due to conflicts between their families. Now, every time a Pokemon faints, he loses the ability to use physical moves for the rest of that battle unless he faints also to protect another team mate. This restriction carries until the end of the game, as you cannot take off Shelmet's shell.
Restrictions for Quoting (AKA, teal;deerling)
Sorry for the walls of text, when I start making a back story I cannot stop, at all.
Have fun with re-revised Healfodder!