Still thinking about Running and Gunning. How about a feat tree for 13th Age Characters?
Run and Gun
Adventurer Tier: You do not provoke attacks of opportunity when making a ranged attack in melee. You may attempt to disengage as part of the attack as a free action.
Champion Tier: Gain a +2 bonus to ranged attack rolls made in melee.
Epic Tier: You gain a +4 bonus to saves made to disengage. You may add the escalation die to all checks to disengage.