If it is to powerful for you, don't allow it. Don't convince ICE to nueter it during the rewrite. Somehow I doubt several versions of the same skill will make a final print.
The
original purpose of Spell Mastery was not to alter spells that were cast. The original purpose was to have a catch-all skill that could be used for spells that might need a caster to have a skill to use properly.
You have a spell that transforms you into an animal? Spell Mastery was what you would use to get skill in those animal attacks.
You have a spell that teleports you? You learn Spell Mastery to be able to change your orientation between the beginning of the teleport and the end (i.e. from an standing to crouching, or changing the direction you are facing, etc.)
You have a spell that requires Concentration? Then you would learn Spell Mastery for it as a way to make sure events don't cause you to lose that concentration (i.e. a skill for keeping concentration, even if hit and taking damage).
That was its "original" purpose.
Rolemaster Companion II is where it was expanded into something that allowed for exceeding normal spell parameters. This was a HUGE change to the skill as well as a huge increase to the power of the skill.
RMSS/FRP expanded upon this, and increase the power of the skill some more, and it also codified these changes to a degree, but it also left it completely unregulated in other ways. It didn't require an increase in PP used for the spell, it didn't specifically indicate that increasing the power of the spell also increased its level. Nor is there any limits about not mastering a spell so that it is equal to or more powerful than a higher level version of the same spell (i.e. ranging a shock bolt so that it has a greater range than the next higher level shock bolt spell).
The RMSS/FRP version of Spell Mastery also left out (or removed) the part (part of option 1) from RoCoII where it says that failing the Spell Mastery roll also triggers ESF.....
In short, RMSS/FRP made the skill even more powerful, but without any checks or balances - which also leaves it open to all sorts of abuses. This is not the first time that this topic has come up on the forums. It crops up every once in a while when folks find the skill being abused in some manner.
IMO, this should be an optional skill that a GM can decide to add, not one that he needs to remove if/when he finds players abusing it.