If you haven't already, check out Antagonists, Chapter 2: Baron Geoffroi D’Arques, for more on the noble's perspective of having court wizards. The ToC free PDF gives some idea of what is covered and check out the Inserts. It's a good book but I found this chapter quite useful for some of my Provencal extended design concepts.
I agree that although the Augustan Wizards are in setting dedicated to setting themselves up as Court Wizards to exert their influence that in fact Learned Magicians (and to a lesser extent their Mythic Alchemist variant, perhaps even Cunning Folk) work better. Elementalists esp Medicine oriented ones can work OK as well. To be honest a character with a mixture of some of the traditions powers could work if carefully built.
Obvious MacBeth style realtionships aside I can't see Folk Witches working for a noble - Infernal witches behind an evil noble yes, but maybe that's all a bit Mortianna from Robin Hood: Prince of Thieves...
Gruagach or Trollsynir might work in the appropriate settings... not sure.
As an aside, this is basically what the Redcap and Jerbiton led covenant known as the Coenobium does in Provencal - except instead of the nobles running the court wizards, the covenant runs their allied hedge wizards for similar reasons: low-cost low level magic, lesser longevity potions for servants (incl perhaps Redcaps), unGifted magicians to help coordinate and protect their mundane interests. I've detailed some of the more powerful hedge magicians associated with the covenant in the supplemental material posted over on my blog if you're interested.
The concept of House Mercere using hedge-magic to help support it's messenger and spy network (low level items at minimal vis cost, augmented by the occasional Hermetic Invested Device etc) or even "retired" Redcaps moving into careers as support team hedge magicians with the help of their prolonged lifespans when they're too old to fulfill physical duties is something I touched on briefly with the elder version (+30 years post Gauntlet) of my first example Redcap, Cymena of Rorschach.
IMO there's actually amazing potential to run a whole non-Hermetic Saga using the "Court Wizard" hedgies concept (either in service to a noble or perhaps even in service to the Redcaps of the Coenobium). One of my slow burn projects is a whole alternate Saga based on a group of hedge wizards essentially trying to make sense of the magic left behind in a fallen Winter Covenant...