If a player really wanted to swap his character's profession by any means necessary, I guess I would allow it and take the easy way, allow him to change the profession, keep all the bonuses and skill ranks - and tell him that from this point on his character would permanently need the double amount of
Experience Points to level up.
Perhaps this is cruel, but hey, either the swap is badly desired and this penalty is it worth to the player, or it is not.
Seriously, I can not think of any reasonable explanation why a profession-swap should be made: any character can learn anything in
Rolemaster, given time and
Development Points. I understand a profession as a character's mental hardwiring and his ability to grasp the concept of various skills, be it theoretical or practical. If nothing noteworthy happens, then the rules are clear from the start and every player knows that professions are fixed and plan accordingly.
There was a situation in our campaign when we allowed profession swaps or completely rebuild characters: we changed the rules how magic works and a player lost interest in his dabbler and wanted a rogue. He took his character, rebuild him and was happy with it ever since, no harm done.
If a player without any experience with
Rolemaster realizes that his character was wrongly build and developed, then we allow her or him to make the changes accordingly. Sure, we introduce her or him to the rules, point out the more important skills in our campaign and potential pitfalls, but nobody is perfect, as the saying goes. We call this the "welp's shelter" (or "welp's protection", I do not know what the right translation would be) and there never were any problems with that.
But maybe I am just too narrow-minded.