Why for the love of cheese make this an INT based skill? You are basically saying that only Wizards and Artificers need apply as all the high WIS/CHA based classes get nothing from their stats.
Instead of making it a skill with a specific stat why not either:
- base the bonus on the primary stat of the higher caster level of the character; or (better yet)
- make it a free enhancement where the player gets to choose themselves which stat is used as the benefit.
In the new enhancement process you have multi-choice options already implemented so why not use this mechanic to enable the player to decide which stat they want buffing their spell power? This gives multi-class characters the freedom they want to push their spell power however they wish.
To me this is a no brainer.
It is bad enough that the new enhancement UI means that anytime you want to add a new enhancement or prestige you have to redo the whole thing, but don't go nerfing people as well by forcing them to take stats they don't need. Listen to your players this time and do it right )or at least better) instead of forcing in yet another broken change and then spending years fixing it (like the ridiculous cosmetic system and the still painful auction house).