Ugh. Voting.
I don't have a problem with the Semblance per say, though you may want to specify somewhere how large the coins/ingots are. I'm terrible at super powers lol.
I'm more concerned with whether or not Beacon would actually use iron for exposed support beams - they are a technologically advanced society and they obviously have some sort of steel compound that wouldn't rust like iron does, which would probably be better for exposed support beams than iron. If they didn't use iron for the support beams, then it would negate his ability to climb the tower.
If they did use iron support beams however, then my other concern is how he uses the coins to adjust his trajectory and make the half-circle move that you describe as 'very tricky'. The way it reads, he pushes away from the coin which is parallel to the tower, but your description of his Semblance states that in such an instance the coin would fly away and he would probably fall to his doom.
Feel free to correct me on the trajectory thing though - I may be reading it wrong.