Not only is the wii menu hard to replace (being some weird wii/wiiu hybrid verified when starting vwii), but it would miss most of the point because of differences in connected standby that doesn't include wii-mode KD (wiiconnect24) processing - which, I am not sure, may even be disabled in IOS
If Someone made a homebrew app/channel to access the Address Book and message send functions you could get Wii Mail working on vWii. I've successfully used NWC24 Editor to add people to my address book to receive and reply to messages on the vWii
As it seems this very new Project looks very ambitious and seems to be focused on the Wii.
(Japanese Channels sounds very promising)
Unfortunately no Release until today,so we have to wait and see how it is progressing.
There's an SDK tool by Nintendo that can be used to send messages on vWii, however since it's an SDK tool I don't really want to spread the word about it much. Plus, it's kind of dangerous, and I'd rather have it work on the Wii Menu.