The main problem with supporting WAVs I think is that new users who aren't clued up on audio formats will use it for long sound effects and music anyway (not all users come by the site/forum to read up on this stuff). Then they end up with megabyte-sized projects which take ages to download. If it happens a lot then C2 becomes associated with slow, inefficient web apps.
So I don't think C2 should give you the choice. If you can't choose, you can't choose wrong. Ogg and AAC are just fine even for short sound effects. Even a short 1 second clip I've found is reduced from 180kb to about 14kb with Ogg/AAC. Consider that saving with 10-20 sound effects.