I take issue with the placing of WW Link at 15% over Midna. Not just because I like Midna, either. There are a lot of things that I feel you didn't take into account.
For one thing, you've bought into the hype that WW Link is different from the other Links in any way other than design. You're forgetting that no two links have ever had the exact same moves at their disposal. Arrows, Bombs, and the boomerang are really the only recurring weapons. The first Link didn't have a hookshot or grappling hook or anything. So citing a "different moveset" is bunk. Furthermore, despite the fact that very few Links have been the same as a previous Link, they have all been the bearers of the Triforce of Courage, which is what made them Link in the first place. Nothing else. Thus WW Link is as much a different character from TP Link as TP Link is for OoT Link or the original Link. You may as well consider WW Zelda to be different from the one in OoT, and her transformation would be Tetra, but then that would be silly. Why is Link any different? You could also go so far as to say that the Link who appeared in WW, having starred in two games, is more likely than TP Link. Thus far, TP Link seems to have won out for the representation.
I realize that the precedent for the same character appearing twice in different forms has been set, but in every case where that happened in Melee, the resultant character was either a clone (not supposed to happen in Brawl) or a transformation (TP Link transforms into WW Link? puh-leese).
Yes, there is the potential for a unique moveset, and that's why WW Link sticks around. However, Midna has an even greater potential for uniqueness. She's almost universally loved by Zelda players, she has a background all her own, she's technically a female, and Sakurai is thus far looking to Twighlight Princess for inspiration in Brawl, judging by Zelda and Link's designs.
You mention overpopulation, but frankly, that removed, I'd say that the two characters are at least equal, and your application of "overpopulation" is arbitrary, as is your removal of 15% seemlingly for that reason alone. I'd like to see real argumentation for both characters, plz.
Actually, your application of the overpopulation rule seems arbitrary in most cases, such as Wolf or Bowser Jr., or Lucario, even. It feels like just an excuse to put a less favored character even lower. IMO, this rule should not be applied unless the confirmed character population for a given franchise has maxed out. Thus far, one Star Fox rep is confirmed, three Mario reps and three (at most) peripherals are confirmed, and two Pokemon reps are confirmed. None of them has reached any kind of maximum, IMO.