What I think would be best would be if we do release a new magic system, limit it's expansion to what the lorewriter allows. If it starts to break the bonds of what is strictly allowed and disallowed, an official decision would have to be made by the lorewriter as to what happens with what had happened.
Let's say the rules say no lightning hands, like in Star Wars. Someone bends the rules a little, and finds a way to channel the lightning through their body. That's edging on not allowed, even though it's not strictly in the rules. The lorewriter would have to decide if this could be added into the lore, or if it should not be added into the lore. Over time, magic could be expanded, but it needs restricting, and lore, and explanations for what spells/curses/etc. can do.