Access to all spells dimnish the examination as the game progress, reduce the variety among party members. Increase starting step of learning curve and left less to explore later (if you know each spell from start). You need to learn about all spells, if you dont want to ignore some of your capabilities. Its in contrast to warbook skills, that are design in electing access manner.
solution; let character can cast only spells, they spend skill points at.
Schools of Magic
Six schools of magic are negligible, because caster has access to all of them, again it reduce the variety and lore to mechanic translation.
Lore-wise power comes from 6x deities, spell power of each school depends from piousness towards particular deity. Deities are jealous of each other and reluctantly succor dissenters, which implies that particular character can thrive at only one school of magic.
Solution: Let highest cumulative amount of skill points spend in one school result in bonus +1 level to all spells from that school (can be cast without skill, if we adopt my previous proposition).
Be advised, that as the progress goes the favorable magic school may change. It would represent that at current time wizard is obedient more to the commands and behaviors of specific deity, and neglects others.
Ameythevian are lean towards Illumination school, but they can just obtain 1 level of specific spell. Lachovians has similar situation with Flesh school. Instead let this race can has generic trait to cast all spell from favorable school, as if they cast with higher stat (either Int or Occ).
All race traits should has other, more distinctive effect, than +1 to some skill, that you can obtain through normal progress anyway.