I'm not sure how the holy hell one would market something like Wai Wai World, but a game like that with modern Konami characters would be incredibly surreal.
My imagined character list from various series:
Castlevania: Gabriel and/or any of the DS game characters.
MGS: Old Snake, Cyborg Raiden?
Silent Hill: Murphy (from Downpour), Pyramid Head, Heather
Otomedius: ...as this is already a parody game, maybe no one? Gotta have some Konami Shmup rep though... Maybe Twinbee would work better.
NeverDead: Bryce
Rumble Roses: Zero familiarity with this game, but just so it's not a complete sausage fest
Contra: Lucia, Browny, Jaguar Yagyu or whatever his name was.
Rocket Knight: Mediocre Dreamworks Sparkster (hopefully classic Sparkster 'cause he's actually endearing)
Nanobreaker: I totally forget these people's names. Think one of them, either the good or bad guy, was Jake.
And of course somewhere in there you'd need Konami Man and Konami Girl (Woman?). It'd be hilarious if it were a plot like Street Fighter: the Later Years, where Konami Man rounds up washed-up game protagonists to... I dunno, save the Konamiverse from various Konami villains, with some wacky references to their infamous E3 2010 conference. The final boss would be Hideo Kojima, who seeks to fulfill his nefarious plan to steal all of the Konamiverse's energy, destroying every planet except Planet Metal Gear.
Let's face it, though: Konami is not this self aware and probably never will be.