SR is a binary mechanic that is easily ignored in most cases. Time to fix that.
Spell Resistance now reduces caster level of spells cast against you by (SR - 15), negating them if they reach CL0.
Much like BAB, SR will become a type of secondary stat, with feats keyed off of it to take advantage of your ability to resist magical influence. This means (with enough investment) SR can grant:
• Bonuses to saves
• DR vs spell damage
• A personal Dispel magic effect, similar to iron heart surge
Example Feats:
Spell Resistant [Spell Resistance]
You are less likely to be affected by certain spells.
Benefits:
•SR 10: You gain a bonus to saving throws vs magic equal to 1/10th your SR
•SR 20: Your bonus improves to 1/5th your SR.
•SR 30: You may roll twice on saving throws vs magic, taking the roll of your choice.
Spellshielded [Spell Resistance]
You are especially resistant to a specific energy type.
Benefits:
•SR 10: Choose an energy type. You gain a resistance to that energy type equal to 1/4 your SR.
•SR 20: Your energy resistance improves to 1/2 your SR.
•SR 30: Your energy resistance is equal to your SR.
Special: You may take this feat multiple times, with each one applying to a different energy type
Shake it off [Spell Resistance]
You take a moment to internalize your Spell Resistance to shake off a specific effect.
Benefits:
•SR 10: You may make a dispel check (d20 + [SR - 10]) as an immediate action against a spell that is targeting you (such as charm person). If you succeed then you are immune to the ongoing effects of that spell for its duration.
•SR 20: You may make a dispel check (d20 + [SR - 10]) as an immediate action against an ongoing spell effect that is affecting you (such as a cloudkill). If you succeed you become immune to the effects of the spell for its duration.
•SR 30: You may make a dispel check (d20 + [SR - 10]) as a free action action against an ongoing spell effect (such as a forcecage) 1/Day for every 5 you surpass SR 30. If you succeed you are immune to the effects of the spell (meaning you can walk through the forcecage)