Let Melees equip SOME BASIC Melee Skills, and Mages equip SOME BASIC Mage skills/spells.

That means that melees wouldn't be able to equip any spell (cure, stonesking, spikes, etc...).
When a Gladiator Specializes itself into Paladin, he will learn Cure, and then he will be able to equip it's own Cure Spell.

That, or just let every class equip only Tier 1 skill/spells.

Mor than that it will be bad : /