The fact that, throughout the multiple times it has been suggested, this approach has been rejected, however, is more telling. And the fact that it is something we do mostly for ourselves also encourages a smaller, less cluttered ranking instead of otherwise, because having more unmemorable scrubs that end up getting nommed just because they haven't been in having matches nobody cares about only means we have to do more work for characters that we, as a group, mostly don't give a damn about. It may even be a viable suggestion, but given how past experience has shown it's not enough clout, I think it's safe to say that it's best not to. And being better than VP2 einherjar for plot says absolutely nothing.
If the reasoning behind passing over this kind of ranking in the past has been for the 'externals', then certainly under the current circumstances it's reasonable to consider the view on its own merits and not based on past precedent that barely applies.
The unique class thing is now more a feather in the PCs cap, rather than the basis they get ranked on. If they seem borderline material, that unique class idea may push them over just based on the interest scale.
Someone like Jill of FE9 got this for example. She's used enough, she has some plot, though its still quite limited...the Wyvern thing just gives her that little extra push to be ranked.
Flipside, Nephenee didn't really get ranked cause she's a Halberdier; what got her ranked was she's an actually interesting FE9 PC due to Wrath and lots of people use her. If she were a Swordmaster or a Warrior or something, I wouldn't be shocked if she still got ranked. The Halberdier thing, in this case, was mostly just "She lacks redundancy" so you couldn't hold the argument against her.
Then again, we ranked both Oscar and Titania, both Paladins (and they can both use Lances, for all that Titania is Axe primary); reason being that they're both early game PCs that many people use and they have plot to justify it. Rolf/Shinon didn't get ranked, despite being unique classes, cause most people just don't use them; Rolf's underleveledness is a massive turn off, considering he's an Archer, and Shinon is just horrible when he rejoins.