Read it all first before you shit your mouth. So we want people to be able to 'specialize' without actually limiting their gameplay choices through hard lockouts and such right? Here's my idea that may need slight tinkering. Attunement would be a stacking buff that could either be permanent or temporary, each time you cast a spell from a school you would gain a stack of this buff for that school or if you already had an attunement to a different school decrease that one. Each stack could grant 'x.xx%' increased effect in that school's spells. So that whole decreasing thing I said before, what is it? Well my current preferred method is to have different schools than the one of your current attunement causing a decrease in it by 'x'. Except for the opposing school which would completely eliminate your current attunement. The number of stacks, duration of the buff, % effect gain per stack, and decrement amount for using other schools are all up for debate.