New position training

Some one correct me if I'm wrong here as I'm not too knowledgeable on the game mechanics. Say you have a new regen that has 2 positions Natural CB and accomplished CM, he has quite attacking stats so i think training him in CM would be a better position for him, so i change his "new position" to CM and as far as I can tell this takes away from his regular training (understandable) after a couple of weeks/months playing and training in the new position he becomes natural and yet it still takes away from his other training, and if I take off him training him there since he is now natural it quite quickly reverts back to accomplished even if I continue to play him week in week out in CM.

This just doesn't seem right to me, I know there has to be some control as if as soon as they where natural and you could take them off with out any repercussions then you could end up training players to be natural every where in the park. Surely it would be more reasonable for players to retain the natural position if they are regularly playing in that role without the need to constantly waste the 10-20% of their training.

I think Maybe a mechanic that looks to see if they are still playing in the "new position" so if they play say over 60-80% of the minutes they spend on the pitch in that role they wont lose the natural position even if they are not training there any more

Any one???