Well sure it would be fun. for about 15 seconds. After the novelty wears off you're left with a long period of complaints. Seriously how long would that be fun? Even if we say, okay no customs everybody plays standard I'm pretty sure namco doesn't want people to think of their characters as cheap and inter-changable paper dolls. Their weapons are sort of iconic of them from identification, marketing and gameplay perspectives.
And as a personal note I never want to see:
Poster one: "I main taki but I use her with a sheild and sword, this Soul Calibur VI artwork namco released is total bullshit. She's got these two little knives. OMG this is so gay. What is she going to do with those? Pick her teeth? I'm going to write president Palin and tell her to fix this."
Poster two: "And why is Mina using a stick thingy? Everyone knows it's the WORST weapon in the game. SHE'S SUPPONSED TO USE NUNCHUCKS! HELLOOOO? Total gigaTROX, Namco-Bandai-Sega-Activision."
Poster three: "No need for profanity man, it's not totally TROX. I trust Ed Boon on this one. I just hope the game hits before next summer. It gets to about 150 degrees here in Tennessee and you know how all EA consoles like to spontaneously combust loz loz. It's hard enough on us when the tide comes in."
Poster one: "I heard they're nurfing nunchucks in this one."
Poster two: "OMD!"*
*- OMD is an interchangable term for the less offensive 'Oh My Deity' for the religious and 'Oh My Dawkins' for secular use."
For a number of reasons. Remember this is a distopian future we're talking about here.