Well one thing I've been wondering is, with all this argy-bargy about the KC-135 replacement competition, why not just forget about both 767 and A330 tankers and develop a KC-17?
Except for the flying boom, I would've thought it'd be pretty straight-forward to put tanks/bladders in the cargo space and plumb up the wings to do hose-&-drogue work.
Suddenly, you have a multi-role jet aircraft able to operate with great versatility and able to convert back at short notice to provide extra airlift capacity. Per-airframe cost also comes down as you're getting more off the same line. Also benefits from crewing, maint, stores & spares and in-theatre infrastructure aspects.
It seems to me that the 707 and C130 airframes provided similar multi-role benefits to the US military (eg. tanker, special transport, AWACS, JSTARS, TACAMO; transport, tanker, gunship). It seems strange to me that the same arguments don't stand with today's equipment.