Have you ever considered adopting the "Friends and Rivals" system from Metroid Prime Hunters? In spite of being a rather poorly received game, it had the best friend-code interface in a Nintendo WiFi game to date, basically being the same as a standard lobby system for anyone who was your friend and rival. And on top of that, if both players agreed, they could add eachother as rivals without exchanging friend codes.
I haven't seen a NWiFi game top this system. It'd be lovely for it to make a return, especially if the bugs were ironed out and the matchmaking service/hosting options were improved.
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Again guys its never a problem of what we WANT to do. Its what we CAN do. I think the MP system stinks compared to something like STEAM or xbox live. If it was up to us it would be just like STEAM, but we can only do what Nintendo permits. We WANT it to be awesome. We DONT want friend codes. But just because Nintendo does it first party doesn't mean they're going to give 3rd party permission to use it.
Believe me, we will use the best best best system we can working with the constraints we are given.