Will Wii Miidia be able to play movies from another share in the net?
Either by:
- daapd / iTunes sharing
- upnp
- nfs shares
- samba shares

or something else?

I am willing to help out there -- Linux and programming skills are existent
I could probably start off with the geexbox code as yours is not available. However: If you think it would be worthwhile to work on something there please comment on it.
If at least one of those methods will be available anyways, even better
Cheers