Those weapon and armour materials are all straight upgrades over normal equipment, which gives me an idea. What if we do the same thing with wands and staves? Suppose that only a masterwork wand or staff can benefit from the item's advantages. Then we can equate normal arcane foci to iron equipment, and the masterwork foci to the various advanced equipment. That would theoretically put martials and casters back on the same level.

Suppose, something like this.

Normal wand or staff: Works as any arcane focus. No additional effect.

Masterwork staff: All spells you cast are upgraded as if they were cast from a slot one level higher. You must be holding the staff with both hands to get this benefit.

Masterwork wand: When you use your action to cast a spell, you can cast another spell as a bonus action. This bonus spell must be either a cantrip, or of a spell level no higher than one third your highest spell slot, rounded down. For example, an 11th level wizard can cast 1st and 2nd level spells this way. It must also normally have a casting time of 1 action.

This is powerful, but it doesn’t seem immediately game-breaking to me. The staff is a straight boost, but not that big of one, since upcasting generally isn’t as effective as casting a spell that’s actually a higher level. The wand might open up some shenanigans, but the bonus action spells only go up to 3rd level at the most, so it’s not world-shattering.

Then again, it's late and I'm tired, so maybe this is a dumpster fire. Just throwing it out there.