Returning to the scheduled broadcast, the cost of fitting booms, operator stations and remote vision systems to airline-type aircraft (except for those which already have a modification available, such as the A330 and KC-767 / KC-46) is very considerable. People have occasionally asked Omega whether they looked at it, but the €millions needed was the reason why not! Had they deemed the cost/benefit positive, they would probably have invested. But they're run by a very shrewd CEO and he would have needed to see a very sound business plan before doing so.
KenV, I can't recall what you flew in the USN - or when? But if it meant you did some KC-135 BDA jousting, I'm sure you'll know what a PITA that was. As I mentioned earlier, the Italian Tornado force launched 8 jets on Night One; one turned back quite early as it had a problem, of the remaining 7 only 1 was able to prod the KC-135 in the dark turbulent conditions. That brave crew pressed on as a single ship, but were subsequently shot down and taken captive.
On the topic of MRTTs, if a true multi-role tanker still has an availability to carry any cargo with full tanks, the obvious question would be why didn't the designer fit bigger tanks? So that with normal crewing and no cargo, the ZFW would be such that full tanks would take it to MTOW. The trade-off between cargo mass offered and fuel required for the AAR mission has always been an interesting exercise, particularly on trails when the AT planners and AAR planners might not always have seen eye-to-eye...