Absolutely right Nsis, Shoving a player into a central position is not just about using the players abilities, it presents the player with a whole set of new things. First and foremost decision making, out wide, very few decisions to make, centrally, I'd say your ability to read the game will get exposed if its bad. Its one of Modric's abilities not spoke about too much, and any top MFer does this naturally imo, you can either see whats on, or you can't. He knows when to pass, burst forward, or switch it. This is what Bale will need to do to be successful there, bringing me back to things that aren't always teachable.
I can understand why Harry wanted to try him in different roles, he's potentially dangerous anywhere on the field. Of course, you're right, he's no midfield general. His strengths are his pace and power. His crosses are usually spot on, too. I'm sure that given time he will add more weapons to his armoury. I doubt, however, that dictating midfield play will be one of them.