Ok so I think the gunslinger should pick a path:
Musketeer (melee weapon and pistol)
Two Gun (pistol in each hand)
Marksman (sniper with rifle)
My idea for the Two Gunner is he should work just like a monk, ie attacking with either hand doesnt matter, left right, whatever its still the same.
He should also get a limited flurry, maybe a deed that requires grit, this way he can fan pistols, or shoot and drop single shots like mad with both hands at the same time...it could be called Blazing Barrels Deed.
Yea its flurry with a full BAB class, something monk-0-philes have been beggin for forever, but it costs grit to do it, and there aint much to go around. SO it should balance out.
As far as the ambi dexterity, left gun right gun whatever (essentially a free two handed fighting) that should be active all the time and cost no grit.
Maybe these should be deeds and not fixed combat styles like the ranger, this way theoretically a gunfighter could take both marksman and two gun (for example).
I think at least this deed would be A) worth the grit, B) fit the theme and C) at least do something for the abysmal rate of fire that the gunslinger suffers from (plus it'd be really really cool.
Marksman, I think they should get gunslinger level added to damage on a single shot.
Im not sure about the musketeer path, what they would get... but something that helped that theme along. Still thinking about that one.