playing a similar concept right now actually. I had just watched equalibrium and I got the ok from my GM to convert the zen archer into a zen gunslinger. He's only trained in the pistol and most people end up thinking I'm playing a weird musketeer concept sans sword.
The only major change (aside from the weapon) was the loss of the flurry of arrows ability (hard to pull off when you need to reload between shots), we replaced it by adding the gunslingers trick shot deed to the ki pool at lv 7. The fact that I'm only playing a single class makes it a lot easier to develop the advanced abilities it seems like every character ends up needing towards the end of the campaign.