- More face building options - I know Nintendo claims there are, like, a gazillion possible unique Miis to be made on the Mii Channel, but despite the wide array of selectable facial features, there are still some important things missing. The first thing I noticed when trying to make a Mii version of myself was the lack of sideburns, meaning my Mii doesn't look a lot like me. Some of the other face parts, like the nose, lips and eyebrows, could also use more options to choose from.
- A Mii Lobby - Why is there no way for me to share my Miis with people besides those who I actively register as friends? I want to be able to free my Miis to roam the world at large, and I don't mean by uploading a picture to some online clearing house. And I want to be able to download Miis from strangers who choose to share them in some sort of Wii-accessible, searchable online database. I know your worried about little Johnny coming across a Mii named "PenisMan" or something, but parental controls can prevent this from being an issue.
- Editing others Miis: So my friend makes a Mii version of himself and sends it over. It's perfect in every way, except the mouth is a little too high. In an ideal world, I'd make a quick edit and send it back to my friend, possibly with a note making fun of his low-hanging mouth. Instead, I try to edit the Mii and get an annoying message telling me "you can't edit Miis you didn't create." I can understand not wanting to let people plagiarize other people's Miis, but it doesn't seem too hard to add an "originally created by" area to acknowledge the original Mii creator while still allowing for people to build on the works of others.
PS3 delights vs. PS3 annoyances
Wii delights vs. Wii annoyances
Xbox 360 delights vs. Xbox 360 annoyances