When I first read this topic I went home and rolled up a low magic vivamanser. One of my thoughts is to take away middle magic but keep cantrips but at double pp cost and only avalable to a character class that has spell casting abilities. Next I gave him rituals with pp costs that did not excede the ranks he had in rituals they were minor healing, plant healing, neutralise poison, cure insanity, plant groth, and study target all at base effect. I gave him a couple of ranks in runes and potions For runes i would double the pp needed for making them and for potions I would only allow formula potions and they are only good for half the time unless the caster learns a ritual to stabalise them. Also in a low magic setting all materials have half there mana potential so you need twice as much for potions and charm craft. We have some house rules for charm craft. First we use loot rules, and since loot doesn't limit how many charms you can make our rule is that a character knows one object and one action aspect for every three ranks so if a character maxed out his charmcraft he would have to be about 30th level to have all objects and actions so he could be proficient in some charms and it would take a while to be master of all. Also it takes 20 ranks to make fetishes and 40 to make talismans. I gave my character 6 ranks and took the actions of heal and defend with the objects of mind and body. Since a pure casting class doesn't have spells I would give a talent that would give a +10 to one skill in the mystical category at first level and an additional 10 every fith level not to exceede +30, for the semi casters (harpers, rangers, warrior mages etc...) half the bonus. Lastly since my character is rather useless in combat I gave him staff and double strike style since it is a very good defensive style. Also since casters woln't be casting spells in combat some type of light armor may be nessesary to survive.