Suggestions:
- - Unarmed strike, querterstaff and kama can be used with the monk ability called Flurry of Blows.
Using the said ability grants you extra attacks at a cost of decreased Attack Bonus. The extra attacks are not applied if your character is wearing an armor or carrying a shield, though the attack bonus decrease still sticks. The number of these bonus attacks increases by one at monk level 11, and the attack bonus decrease decreases from -2 to -1 at monk level 5 and dissappears at the level 9. - - Getting one level of monk grants you some decent unarmed feats for free and gaining monk levels in general improves your unarmed strike damage.
- - Fighter levels can be used to gain extra feats when necessary and to get almost every profiency feat there is for free.
I'd get the strength and wisdom ablity scores around 14-16, while raising the dexterity score as high as possible. This doesn't necessarily mean you have to have constitution, charisma or intelligence as a dumb stat, but for this build charisma and intelligence are less needed ability scores.
*As for the feats, I presume it is a plausible goal to reach level 20.
Weapon Finesse: You are going to have high dexterity, with this feat the ability score will improve your unarmed strike, kama, and shortsword attack bonus.
1 Feat.
Two-weapon fighting feats: I would not try to get the the Two-Weapon Defense feats, so focus on the Fighting ones.
3 Feats.
Archery: With the bows that do not require ammunition - you can buy them from Jezebel(Spelling?) in the Great Bazaar - archery is little less useless. Nonetheless, Point Blank Shot and Rapid Shot are decent feats to get for any ranged character. Improved Rapid Shot really improves the Rapid shot, but unfortunately it requires you to pick up the Manyshot feat first which is almost completly useless feat. The only use for the manyshot feat is when you cannot hit your opponent unless you roll a natural 20.
(If you need to roll a 20 to hit something, it simply means that your AB doesn't have an effect when it comes down to hitting the foe. I would try to pull off as much of damage as possible on those rolls of 20. (Manyshot and Power Attacks.))
Unfortunately I do not think there are returning Shurikens. Nonetheless it is worth to mention how monk can use Flurry of Blows to throw shurikens. Thus, Monks get free Improved-Improved Rapid Shot for free.
4 Feats.
Power attacks: If your character is wielding a weapon with both hands, go for the power attacks for extra damage. Power attack feat is required for the Cleave feats, those feats grant you extra attacks when you kill something. The benefit from Great Cleave is arguable if your character is not capable of pulling one-hit-kill-criticals.
4 Feats.
Combat Expertise: It requires that your character has an intelligence score of at least 13. Instead of damage it improves your AC.
2 Feats.
Weapon Proficiencies: You get bow and shortsword profiency from your first fighter level. For Katana You need to pick Weapon Profiency (Exotic).
1 Feat.
Thus, to get all of these feats you need to get 13 feats by the level 20. Natural Feat progression gives you 7 feats by the level 18, so we need 5 extra feats.
You get those at levels; 1, 3, 6, 9, 12, 15, 18, and you get them regardless of what class you coose to level up your character as.
You get fighter bonus feats at levels: 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, but only if you have the required amount of fighter levels.
So, we go for 11 levels of monk, which leaves us with 9 levels to play with. From what I've listed we can spot how you can get the needed extra 5 feats with 8 levels of fighter and thus we got the the required amount of feats by the level 19.
Take notice how "Humans" get one extra feat and some skill bonussess.
Yes, it is not the best character around, but it is indeed do-able and not utterly useless. It isn't able to reach the insane criticals or smites or sneak attacks some other builds can, but it should be alright and able to level just by on it's own.
(Not to mention being a lot more interesting character than those cookie-cutter-scythe-wielders without enough depth to form a pond, if it happened to rain on them.)