Awesome idea. It would need to have really detailed stat tracking, both weekly stats and all-time, and then send you a congratulatory message on the messageboard anytime you rank on a list or pass some all-time kill milestone. It could also reward you for certain acheivements with secret agent or commando getups for your Miis. The game would have to restrict you to only using Miis created on your own Wii, though... And Nintendo would probably want to have some sort of censor on Mii-names, but given the limited name entry space, thats actually feasible.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
