I think it is a good choice for him to train for BJJ, the point being that even if he only does GNP he will be on the ground a LOT, and will have to avoid the submissions of others while he is there. As for striking, he should really try to improve there and should mostly focus on defence, not offence, and should be shown how to tell when it is a good oppertunity for a takedown. I have seen so many wrestlers go for takedown after takedown when the other fighter is just waiting for him to come in for it. With there being no real record of his chin, it makes me wonder quite a bit. Simply put, his training should be VERY well rounded, and shouldnt focus too much on ground game.