So? Are you telling me a monk can't fight with swords? Not every monk needs to fit the unarmed zen master stereotype perfectly......
No. Serpent Fang works only with unarmed strikes or monk weapons. A greatsword isn't an unarmed strike or monk weapon, unless there's a feat that makes it one. Or I might give him a gargantuan longsword and the Lighten Weapon feat, but then it's another feat slot used and he's going to have a penalty to attack.
Again, so? You're trying to get more reach than an average huge creature, right?
Deformity (Tall) requires being medium.
Also, consider switching your weapon for Spinning Sword (Secrets of Sarlona) it has reach, thus doubling your reach and is still mostly a sword.
It's too different then what I need. I need a normal looking sword that can be fluffed as a katana. Spinning sword is too weird looking.
And I know that I'm asking for optimizing his reach, but doubling his already impressive reach would be overkill.