Probably it would be easiest to avoid any negatives at all (so as to avoid having to mod the code, which does seem messy/difficult).
So how about:
War Fan -> Tieshan (0)
Lajatang -> Spade (+3) or Chan (+4)
Wakizashi -> Shuanggou (0)
Daikyu -> Dagong (0)
Nunchaku -> Chui (+4) ...although I would disagree with this exchange, since nunchaku are fast striking weapons, while chui are very heavy
That still leaves us with Bo, Shuriken, Sling still...
If Nol is willing, and believes the name changes can work, so long as we're under the original sum total lengths, I'd rather try it that way, first. (I'd particularly be sad to lose Pellet Bow and Staff.)
In exchanging Nunchaku for Melon Hammer (or Chui), I don't think UA weapons reflect effects to speed or initiative, do they? I thought Melon Hammer might be a good choice for replacing Nunchaku as they are both blunt weapons and the Hammers could then be used in pairs (one in each hand), IIRC in OAUA. (Melon Hammers are usually used in pairs by practioners.)
I figure that maybe some players might miss the Nunchaku, but they were pretty rare to Chinese martial arts until Bruce Lee's modern-day movies of the 70's.