But at least in the second option that Majin presented, there's a deal of precedence. There is currently a player with two Navi that act independently of one another and then there's our dear friend Rass, a Navi with 4 individual identities floating around in him. So long as the weapon is incapable of moving or acting on it's own except in cases of signature attacks, I see no reason myself to rule it out. Granted, I'm no mod, but by looking at the past I see few reasons why it would not be allowed.
Really the biggest problem you're going to face is showing that this is your own idea, or better put, making the idea your own. Just seperate it from the Bleach version and you'll be fine. After all, there have been plenty of talking swords, not to mention other weapons, over the years. I'm sure there have been cases of individuals inspired to use something based off of Dungeons and Dragons and sentient items are seen often enough in it. The whole, learning from the blade, thing, might be a little hard to pull off, but I can't say exactly how so. I've actually never watched an episode of Bleach myself, so I suppose it would have to do with how closely the personality of the weapon resembles the other, or something similar at least. At the worst, you could ditch the 'learning' thing and I'm fairly sure it would pass. As is, it doesn't seem too bad. Again, I'm no mod, but I fail to see where it would, well, fail, heh.
One last note, a snobby brat of an operator? My, Sin was rather accurate in his statements about our similarities, heh. What's that old saying, great minds think alike? But that's just my ego running amuck.
Again, you'll have to wait for a mod before you can get any definite answers, but it doesn't look bad. If you've got your character's set up, personality and definition wise, and you're familiar with the character creation process in rules, I'd suggest you just make a new topic in the new users thread and hope for the best. That way, if there are any problems beyond your weapon and it's personality, well, you can get those extra problems out of the way as well.