I don't like the idea of capping magic resistances, or at least not at anything below 100
I'deally, It would be nice to see it done Final Fantasy style, where your elemental resistances could actually go over 100%, causing that type of damage to heal, instead of harm you.
Eg, with 110% fire resistance. Whenever you're hit by a fire attack, you would recover 10% of the damage you would have taken at 0% resistance.
When applied to special damage types in combat, it could put a negative strength modifier on the enemy. Ie, frostlings (2 base, 1 cold strength) against someone with 150% cold resistance, would result in subtracting 1.5 from their strength (150% of the 1 cold strength) before any modifiers like promotions are calculated.