I tried Gun-Fu for a bit, it works well enough in PvE but generally got hammered in PvP cause everyones accuracy was far superior to yours.Go a devoted ascetic, vitality isn't that needed. Spread your stats out evenly between Belief, Perception and Focus, if you have 1 point spare put it in focus.Dual Pistols is the best for this, lots of moves in interlock, use Kung Fu cause of it's flexibility and it's large range of state specials.Cause you are using both Guns and MA I found the operative buff served best, so there is no reason to load up to a level 50 title buff. My loadout was basically a beeline to Dual Pistol Execution and a beeline to Wooden Dummy Drill, with a few other abils picked up on the side, Piston Kick and Pistol Barrage I think.This loadout was good for beating MA's, cause guns>MA and also good at beating hackers cause MA>hax.
9mmfu has said, his normal (as in non-Admin character) level 50 character has stats of 20,20,20,20, 11 (or was that last one 8?) With that you can switch to any tree and be reasonally affective, you wont have best damage/accuracy but you will have better protection from other tree's. It would be a lot more ill-advised to load up a hybrid then though as your accuracy/damage wouldn't be worth mentioning.
Personally, I am a gunner, I do little PVP but with the Yuki Dana/Area K/Quicksilver gloves, and as most NPCs use guns/hacks, I can clear the biggest busiest mission area single handedly without a single thought of health.
I've been running as a Karate GM / SMG Specialist for a long time now... and what these guys have said pretty much hits the nail on the head. It does have definite advantages in certain situations but for the most part, especially in one on one PvP, the accuracy you lose by splitting between the two trees is too big of a penalty. If you PvP at all with a loadout like mine, you really have to accept that you're going to be more of a supporting player than someone who can go out there and do overly well by yourself. Either you'll need others to help you dish out the damage and buff you, or you'll be the one doing the assisting.
That said, go with what makes you happy. You will find some success, particularly in PvE, with a mixed loadout and I know (for me anyway) combat just wouldn't be fun if I was running with something strictly because it wins me fights instead of something I enjoyed using. Besides, it's always great fun to have someone see you con as a Karate GM and think they can root you and solve all of their problems only to get hit by a Full Auto Redux.