I like these. A few more while we're at it.

Alignment: Determine your natural mana type if it's not otherwise known. Commoners, thieves, and barbarians can pick up this feat for free after heavy arcana investment. May limit guild selection for commoners.

Mana sense: Gives tuner effects without requiring a tuner. One feat per spell type.

Sacrificial arts: Allows you to fuel spells with spirit. Used as a symbsiosis while prepping the spell. Heavy cost reductions with RP text if you have Memory of Nature or holy warrior active.

Advanced sorcery: Reduces the backlash rate of all spells to TM/Debilitation levels, or makes your most difficult alignment the same as moderately difficult alignments.

Primal sorcery: Teaches magic users how to use a berserk or khri, from a scroll. This requires berserk or khri scrolls to be added to the system.

Advanced artificing: Enhances artificing products to make them useful. Nemmiro stones now last until you leave the room. Runes have a 95% chance not to use charges when rubbed. Mirkik sokis and aura devices now lasts until you die or 24 hours. Devourers follow you around and are destroyed when you log out. Bubble wand now also casts air bubble on the invoker, which lasts 3 hours.

Meditation: Opens up a "perceive magic" option which works for spell casters the same way khri meditate works for thieves. It trains you a little bit for every spell you currently have cast on you. Moon mages get the additional perk of learning when they perceive others, and they get this feat for free.

Artificing affinity: Greatly reduces the arcana requirements to use enchanted products, because terts should get to use magical devices too.

While we're at it, how about a few more generic AP spells? Wards, utility spells, attack types, and the like.