I think it is a bad homerules addition, at least given your stated objective.
As other people said, your modification hits T3 and T4's a LOT more then T1's.
Many Fighter/gish/rogue types rely heavily on UMD, Wand Chambers and "spell consumables" to stay on par with full casting classes. This means that you will nerf these kind of archetypes instead of the ones you are actually trying to.
If you want to really hit them, take away the rule "Spells from scrolls are cast at the CL of the caster, if it is higher then the one of the scroll", limiting heavily the real advantage full casting classes have over other archetypes when using scrolls.
Bad idea. Everything the PCs are not allowed to have should not be permitted to baddies too. BBEG is excluded since he has his separate role, but these classes are not fit for a BBEG anyway