Off-topic:
The online support for Nintendos stuff is farking appaling. I bought that USB connector, and I've barely used it. Friend codes? wtf is up with that?
I hear a bunch of people saying similar things about WIFI but I've really enjoyed my experience of it in Mario Kart, Metroid Prime Hunters, Star Fox Command, Bomberman Land Touch, Gekitou Custom Robo, Tetris and especially in Animal Crossing.
Admitedly without friend codes you'll inevitably run into people who a) are frustratingly good b) rely on exploits or c) just plain hack. But if you've got a few friends who own DSs somewhere in the World then you can have a lot of fun with friend code battles....I dunno maybe that's just me.
Incidentally, not all games are plagued with problems like these: I haven't heard any bad things about the WIFI in Club House Games and Gekitou! Custom Robo hasn't fallen prey to exploits or hackers. There's nothing wrong with getting an ass-kicking from someone who is genuinely better than you at the game.
On-Topic:
Yeah a WFC version of Advance Wars would be brilliant and I think the developers would be insane not to include it if and when they make another sequel to this long running series. On a similar note I'd love to see a Super Robot Taisen game in English on the DS with WIFI...now that's something to wish for (although I've no idea how it could be balanced).