As long as the 7E7 airframe is appropriate for tanker use, I think this might be a good choice for a new US tanker.
The US military could probably use a good long ranged mid-sized tanker/cargo/personel transport, as these aircraft would probably be multi-use in the same way that KC-10s are now. The US military often ponders its needs for more airlift capacity, and this mid-sized aircraft could be ideal at this role, leaving the C-5s and C-17s for handling the outsized cargo. The 7E7 would probably be easier to maintain and upgrade than a soon-to-be out of production airframe like the 767. BTW, I'd love to see how they install a cargo door in the side of a composit airframe.
It doesn't matter if the military or a civil airline lauches the 7E7, a customer is a customer. I'd love to see if the WTO can creatively come up with some twisted way of seeing this possibility as "uncompetitive", as 50,000 plus pages of the GATT treaty leaves a lot of room for imaginative interpretation.