Ninja..

[Masa]

The Katanas/Shurikens are ridiculously hard to balance, given the expectations:
- Only 7 Katanas are allowed
- Ninja can ONLY use the Katanas or the Shuriken

This being said, besides 7 Ninjas, every other member has to use shurikens. They physically cannot use any guns whatsoever.
When they're against other gangs that are able to use any gun(including PBP, Crizens, etc), they are put at a disadvantage. Not to mention they don't have the over-the-wall-firing convenience of an SD-Cannon or AC.

Stat-wise, it's really easy to either put them at a disadvantage by limiting them to shurikens with a reasonable firerate, or put them at an over-the-top advantage by making the shurikens ridiculously fast.
Throw in the katana, then you have another parameter to deal with.
Because seven of them have powerful katanas, should the rest of the gang be punished with a slowed-down shuriken? If the shurikens are fast, should the katana be slower and less damage? Because they're only limited to those two weapons, should they all be allowed a katana?
If one of their only weapons is allowed in the event shop, should it have better stats if they're on Ninja tag?
Any decision would warrant a complaint. You can't please everyone.
Currently, nobody is pleased.

Ninjas: These shurikens and katanas suck! We need more shuriken speed and the stun feature added back to the katana!
Everybody else: Their shurikens and katanas are too strong. You need to nerf them because they're too fast and too powerful!

Realistically, it's completely circumstantial.
They're fine in closed areas and when the ninjas outnumber the other gang, or where the opposing arsenal doesn't consist of SD cannons, PBP shotguns, Crizens, etc.
Otherwise, they're at a disadvantage.

The logical(and perhaps the most controversial) option would be to give each gang their own tailored arsenal and limit them to those weapons only. This would not only make each gang a unique, theme-identified unit, but it would add a more "turfy" feel to gangs. It could also give people more incentive to join a gang, perhaps even be more loyal to the gangs they're in. Not to mention, it would be much easier to balance.
The con, of course, would be how to get to that stage. That would require pretty much every gun on the market to be deleted, and new guns to take its place.

Don't be misled into thinking that I'm suggesting this, but given the current situation, the playing field could only be soundly level with this solution. The alternative, of course, would be to completely scrap the Ninja idea and revert back to ALS.

Personally, I'm for GC's gang idea.