Sorry Glenn, I don't see this yet. I am parsing すぐやりたがる人 as
すぐ + やり-たがる + 人 = "person who likes to do" + adverbial すぐ
In this interpretation I am not very clear what sense すぐ has, though I understand it to be adverbially describing the way in which the person does, or likes to do, the activity. Am I parsing it wrongly?