The mage hunter, I would tie back to their BG logic.
The "Agent" version:
Like a mage hunter tied to a church, ala the inquisition, I'd base on the Witch Hunter concept. . .so a ranger in base concept, channeling base, using variant anti-magic lists.
A Mage hunter working for a guild, ala an enforcer used on guild members or freelancers in guild territory, I'd call Essence, based on the Monk costs (Or convert the warrior mage as a template)
A Mage hunter working for a mentalist circle would be mentalism. I'd use the Magent (Or the Bard if you don't want to do that)
As to Solo hunter, I'd likely use variations of the above, depending on how they learned magic, and what their source is.
As is, why not just use Brent's converter to convert their costs over directly, then use the lists from the book, directly?