I have more ideas for a Gunslinger class than could ever be practical to use all at once.

My initial thought would be to base the class on the warlock chassis but bumped down to a half caster (3/4 caster? IDK) to make room for something that looks something like the Paladin's Smite ability and some other abilities (in my case based loosely on ideas directly from the Dark Tower books). Invocations is the design space for both spell-like abilities and perhaps some combat related goodies similar to Blade Pact and/or some of the combat Feats (modified, obviously).