I don't think it should be a Smash Bros. clone because, well, it usually just gets ignored, so, yes, maybe it can be a platform fighter, but i always felt, attached more to the idea of it being like, a more standard 3D fighter, closer to Fighting Vipers, not Virtua Fighter for sure, but then, i don't think it'd be too Klonoa, i think if a fighting game would exist, it really needs to lean on the fact that it is Klonoa, otherwise, why play this over, well, another fighting game that does all that it is trying but better? So i guess it being a platform fighter would be wise to complement more on Klonoa ideas, I think everyone should have a ring in this game, may sound odd, but it'd be comical, and kinda funny maybe.
Perhaps have a Street Fighter Alpha 3 A-ism and V-ism thing, like, you pick Lolo for powering the ring as if it was V-ism, or you pick Hewpoe for powering the ring as if it was A-ism, have enemies spawning on the stage and such, but i don't think it should have the Smash Bros. system of % and having to knock some one out of the stage.
But if it is this, i think it should be a side-game within a Klonoa game.