I'd like to make a few suggestions....
Well, regarding the rankings, I think that Ryu4 needs to drop to 3.0 instead.
He doesn't really get going till about Floor 2 or 3, and his game HAS a level limit of 50.(Besides Fou-Lu)
After Floor 7 or so, he doesn't get any more powered up than he can be, and dragons giving him extra life bars aren't exactly that useful when he doesn't have the AP to last without full heals.
And Virginia probably should get ranked at 4.5 or something. Look at what Snow did to those poor floors before Floor 7.
And now for a few ranking ideas....
Fou-Lu 4.0(BoF4 PC)
Pros: Begins with Royal Sword. Gains first Dragon at Floor 2, with good MT, reliable ID and Aura Smash from Tyrant is ITD. Faster than his boss forms by a large margin.
Cons: Has MP troubles if he uses Tyrant, doesn't offer much besides pure damage and MT. His strength tapers off at the aftergame floors, to the point where he's only a really good Heavy.
Levin 3.5(Wild Arms XF)
Pros: Speedy. Broken against slower people like-you-won't-believe. Turn-cancelling works on bosses.
Cons: Hates good evasion, and durability is okay at best. Can run out of MP in the long run, since he doesn't recover after each battle in the Dungeon.
Gale1 2.5 (DDS1)
Pros: ID whore with Wind damage. Has Curse and Stone, which are just BRUTAL status. Also can revive, and near-limitless MP.
Cons: Durability is only above average, status besides ID have bad hit rates, cries if enemy resists Wind and Death. Earlier floors, ID isn't that good, as is only a secondary damage dealer till Mudoon. Lightning and status mauls him.
Gale 2 3.0 (DDS2)
Pros: Tanky and quite fast. Gains HP boosts with his physical Mantras, and eventually RESISTS PHYSICALS. Critical rate is obscenely high, which works with Press Turns for brutal effect. MT charm, confusion and stone physical skills, has good Wind and later, Fire damage.
Cons: Needs to be healed every turn or so if he uses those physical skills. His status hit rates aren't very good, lightning and status mauls him.
Tear Grants 2.5 (TotA)
Pros: Decent healer and reviver. Enhance Cast is just sexy, and so is Holy Song. Has good damage once she gets her Pendant back at Floor 4 or so. Running out of TP is actually a chore.
Cons: Her healing's not full healing, and she's heavily reliant on Holy and Fire damage. TotA status blockers are crap. Force Field interps may vary, as well as her 2nd Mystic Arte. People think spell casters are slow.
And for the heck of it.....
Ash 3.0(Phantom Brave)
Pros: Damage up the wazoo. We're talking about solid OHKO per turn, and near-G.Dragon damage on his Solemn Vow turn. Also has Initiative to instantly take out someone. Durability's quite good.
Cons: He lasts five turns. No, seriously. His damage doesn't get that EVIL until Floor 3 and onwards unless you allow him swords from the beginning. Also, interpretation troubles about reviving him. One-dimensional damage, and Heliotrope is gained late. No MT kinda hurts too.
And for a suggestion for the Sealstones thing...(inspired by Persona 3 and DDS XD)
One More! : OPB, can be used to instantly give 1 member a double-turn on their turn. Reduces available points by 3. (So, it's a little different.... But it's too broken in P3 with that Knock Down and stuff)
Press Turn : Hitting an enemy's weakness nets you a Press Turn, given to the next person to act on the team. Likewise for your enemy. No effect on points.