We will consider iOS, but Windows Phone is very unlikely.

Well, and Ubuntu for phones (Ubuntu Touch)?

1. http://www.ubuntu.com/phone/developers

Consideration can be given a mt7621 scheme, performance is much higher. The cost should not where to go.

I agree.

Mainly NAT64.

DNS64 in as far as possible.

*) NAT64:https://tools.ietf.org/html/rfc6146
*) DNS64:https://tools.ietf.org/html/rfc6147

保持良好的磨破k.