This is where I'm at. Someone here asked for a "gunslinger" a while back, so I wrote them a battlemaster variant (mostly so I could name the abilities things like "True Grit" and "Deadshot"). I assumed the guns were six-shooters that basically acted like hand crossbows, and I didn't include misfires and stuff because I don't like "weapon break" rules. I think the person ultimately opted to use Mercer's PF port mentioned above, because they liked the weapon breaks.Basically: if a player wants to be Roland Deschain (or, heck, Murlynd), I'm happy to let him.
I like gun-based adventure fiction tropes just as much as like the other adventure fiction tropes D&D uses. A big chunk of the stuff usually cited as the inspiration for the game has guns in it. Guns absolutely belong in D&D if you want to put them there.