Is it possible to create a spell that checks primary statistics? For example if a character's highest stat is Intelligence then they get Arcane, Strength gets Blades, etc.? That would solve the diversity discouragement problem. Seems quite powerful, so it should replace Arcane. The problem (assuming this can be done at all) is what to do with the other slots. Cloak of Curses is fine, but the other two become pointless. You could have a defensive one, but that steps into Ward territory.
Perhaps the two in the middle could be personal modifications to the spellcaster. For example, a spell that gives the user Invulnerability, Daze, and Immobility, essentially turning the caster into a tanking statue- Cloak of Stone. (Which I can see being broken with Unshackle Mind. )