Classes for Into the OD&D - Wizard

Vancian magic gives a certain flavour to the wizard that I like but find incredibly fiddly in implementation. I wanted to keep the preparation and memorisation part of a wizard whilst bringing the spell book to the fore and lessening their impact as a combat caster. Here's the proof-of-concept draft as it stands.

Wizard

Wizards study the science of magic. They read the Mystic language that let instructs them in the precise rituals of casting spells. 

Mystic: Only wizards can read Mystic, a script found on scrolls, spell tomes and magical artifacts. Mystic is also spoken as a secret language of wizards and used in casting spells. Understanding of this ancient script lets them defer some meaning from nearly any language they read.

Spells: Found in Tomes and Scrolls. A Spell requires ten minutes per Spell Level of uninterrupted calm and attention to cast, as well as requiring a precise, detailed process. As such, Spells are generally unable to be cast in a combat situation. After casting a Spell ongoing effects last until the Wizard casts another Spell.Cantrips: These simple spells may be memorized upon reading and cast immediately at will. Focus: Every Wizard carries a Focus, typically an orb, wand or staff. Upon casting a Spell the Wizard may also Hold the spell in their Focus. They may now cast it immediately, at will, as often as they wish. Only one Spell can be held in a Focus at once.
Spellburn: Casting a Spell is a draining process and causes the Wizard damage equal to the Spell's Level. At 0HP Critical Damage may be avoided by a WIL Save vs 10.
Starting Equipment: A Wizard starts with a Tome containing all Cantrips and First Level Spells and a Focus of their choice.

Converting Spells
Spells can be converted from any wizard spell list:
- Ignore material components.
- Durations last until the Wizard casts another Spell.
- Saving throws are made vs the caster's WIL Score.
- Caster Level is the character's WIL Bonus.
- Target's HD is their STR Bonus.