As well as being wonkier to pull off, I, myself can't really think of any skills I would be able to logically apply to a Bleach forum game... Are there even that many?
But yhea, with the best part of that idea being the swords turning into better swords, I would suggest just taking... Hmmmm.
I'm just not sure, it seems even the theoretical supports are a bit wonky here, and there's not that much to say about it.
You could get
some mileage out of a Rock-Paper-Scissors style affair, such as where the "Heavy" trait or skill or what have you is strong or weak to the "Light" stat or perk or whatever which is strong or weak to the "Medium" special or move or something. The problem with that is that it tends to be either pretty situational, as you'd get if players just made up their own stuff and so "Heart" was countered by "Despair" but everyone's going to have or be Lightning or Gravity or Speed or Hate or Arcane or Song so the odds of it mattering suck.
Or it tends to be pretty limited, as with the above Heavy/Medium/Light categories, because once you've made yourself Medium... well, then what? You usually win against Heavy and lose against Light, or vice versa, and that's mostly it, right? Do you get a Medium II skill at some point, or something? Branch off into category-specific Counter or Heavy Smash skills, perhaps?
It's doable, but at some point you'd want to just make them stats or special activated abilities or something.
As for making the game more interesting... well, if it's about swordfighting, you'd best make the swordfighting mechanics decently interesting. You could do some kind of RPS style thing as above but with individual moves rather than characters, so you get to guess whether you want to attack Aggressively, Balanced, or Defensively this turn. You could come up with some kind of Armor/Guard/Stamina systems to make sure fights consist of more nuance than "hit thing until HP goes to 0." You could introduce Exalted-style mechanics wherein you get bonuses to your rolls for describing your action well, so that even if the system itself isn't great the game still
looks cool.
Again, there's ways to make it happen, but you kind of need to decide on just what kind of game you want it to be mechanically, and then put in the time figuring out how to make that happen.