The thing about the Koopalings is, usually, if you get one, you get all seven, which is a big chunk of whatever roster that could be dedicated to branching out in other ways. Smash did it right, by making them all alts of the same character. Their appearance on the MK roster, for example, comes off a little like filler, especially when they consistently choose to omit unique characters like E. Gadd, Kamek, almost anyone from DKC, or even past ones like Petey Piranha and Birdo.
Well, they're part of why it feels like filler, the other is the increasing amount of derivative characters like Mario and Peach covered in various alloys or a completely unnecessary amount of baby characters (that don't even use existing ones like Baby Wario or Baby DK).
I really don't get it. The Mario series has such better options to work with. I don't even bother entertaining the possibility of RPG characters getting acknowledged, because that seems like a total lost cause (outside of Smash, at least). But it does make me happy that EPD doesn't create, or really seem to influence the Smash roster at all. Three Links would actually look tame in comparison to their version.
But **** would Geno and Mallow have fit right in to Double Dash perfectly.