Learning moves for pokemon is always done by leveling or giving your pokemon a tm or hm or meeting a special character. How about making powerful TM's a difficult task to obtain. For example take an actual machine instead of an item and a place where you have to travel through a high level area for some time to get to it. Once you get to the TM to use it you would have to pay a large sum of money to leave a pokemon in the machine to learn the move. You have to wait 12 hours before returning and you can only have one pokemon in anyone of these machines at one time. Nothing else besides learning the move happens to the pokemon left there unless of course you wait for an extended amount of time to retrieve the pokemon in which case is may not be as fond of you. There should not be any pokecenters within close proximity to these machines so you would have to have the pokemon with you and it would have to survive all the way to the machine.