The correct way to do this is to strip the powder from the fork blades and braze in a reinforcement or don't drill a hole and braxe on a section of tube to the front or rear of the blade. Powder coating a fork is not that expensive and having a hole through your fork blade, without a brazed in reinforcement is dangerous.

Your aluminum insert idea would protect against crushing, but it still leaves you with a hole through the fork and the insert does not provide sufficient support to prevent the tube from collapsing around that hole. I don't have any proof that this will happen, but I wouldn't be comfortable with doing it that way.