That's not really been proven yet that he isn't clever enough, unless you want to count his brief sub appearances as a sub for us?
As for being lightweight, he's quite a tall lad at 6'2" and can easily add strength/size if he so wished but maybe it would affect his game?
He is definitely fast enough as well, don't know how you can say that when Kris Boyd was top spfl goalscorer last season.
Ryan has had good loans spells and consistently scored goals both at club and youth international level, he's never been given a proper chance here and I'm not sure he ever will but will go on to make a decent career for himself I think, a good Bear as well and a nice lad.