I'm not particularly upset by these even in the Minor Magical Focus range. It only helps with items, and only with items that do something thematically linked to the type of item.
I might, however, make it two kinds of foci.
You could take Minor Magical Focus: Wooden Wands, which would let you cast spells that create or control wooden wands, or whatever, along the normal magical focus rules.
You could instead take Minor Magical Focus: Enchanting Wooden Wands, which would give you a bonus to enchantments on wooden wands provided the enchantments are in line with the shape and material bonus for them.
This deals with the jade issue; you'd either have Minor Magical Focus: Jade, which would enhance anything you did that targeted, created, or affected jade. Or Minor Magical Focus: Enchanting Jade, which would be limited only to enhancing lab totals for enchanting jade items with aquam effects.
While yes, that latter's pretty broad, it's limited to enchantments only. It somewhat lessens the gap between verditii and other magi, but I think House Verditius still comes out ahead of the rest. Tremere is a bit weakened by it in comparison - they'll lack the strong focused enchanters of other houses, and the powerful generalist enchanters and extremely strong focused enchanters of House Verditius, but then, if you read the writeup of House Tremere in True Lineages, their weaker magic is a thematic part of their house that they make up for with teamwork.
At least in my case, this is a situation where thematics make up for a somewhat undercosted ability (getting a focus in a wide range of enchantments for a minor virtue), much in the same way that you get virtue points for taking Personality Flaws that describe the character you were going to play anyway, and for taking beneficial Story Flaws like magical animal companion or faerie friend.
The only problem was, being able to enchant anything in a wooden wand or whatever was a bit much. Limiting it to effects that are appropriate for wands (which the shape and material table covers well) makes it even more thematic, and tones the power down just a little. If someone wants to make a magus with Minor Magical Focus: Enchanting Wooden Wands, and so carries around twenty wands with different spells (which project, control, repel, or destroy things) at all times, I'm all for it. The image is kind of neat, and would really drive home the theme of the character.
Similarly, a magus that uses bits of amber, wands with amber tips, amber amulets, etc. for various Corpus effects would be cool enough that I see no problem in allowing that at as a Minor Virtue.