I know this has probably been suggested before, but I really like the random status effects you can get from the sealed sword, and I hate that I have to trade it off for a more powerful sword. So I was thinking maybe there could be a third line to the seal sword. Something like.
Sealed Sword -> Binded Blade -> Chained Claymore
Perhaps to balance the sword gaining overall strength and a more powerful version of it's random status AoE the upgraded swords might have a random chance to either A) inflict the same status on the user that is released with the charge attack, or B) inflict the same status on the user no matter what power is activated with the charge attack. (i.e. if the sword causes a poison AoE or a Fire AoE the user have a chance to receive a stun status but never any other status. This sword's damage type would remain normal instead of splitting like the existing branches.
The AoE might also change with the upgrade, it could either become a projectile blade like the avenger and faust, or it could turn into a bigger AoE, maybe encircling the user similar to the Fang of Vog's charge attack.
i like your thinking here, theres just enough detail to go by in order to get a good grasp at what you're talking about, and it sounds balanced as far as i can tell. i personally love how you kept the matching first letter trend with the upgrades, very clever~
though its not really a new idea, rather expanding an existing idea, its still a good idea. i like it.