Ewww, Kuno is not allowed to have successful romance ever!
That's pretty much a rule as far as I'm concerned, maybe even a fundamental law of the universe: Kuno shall not be given an opportunity to reproduce.
Well, I picked the three/four I did because I know the series pretty well. I'll admit to not having seen either Bleach or Love Hina. I'm sure either of those would make perfect additions to a ditz pairing, but I can just see really bad things happening with the three I mentioned. I can almost guarantee that I have less than 50% of the anime knowledge of 90% of the people on this forum having focused on video games waaay more.
Plus, they were all blonde, and they all really exemplify blondeness.
I was initially going to say Asuna from Negima would fit in well, but she strikes me as being too motivated.