Wow-after an initial -maybe-dozen a WHOLE extra 10-20 airframes-I am sure that AB and Boeing will have their R&D teams burning through the overtime.
Yeah, neither of them would be interested in relatively minor tweaks (an Aux tank and strengthened gear may be all that is necessary...) in Airframes already
ALMOST capable of doing what is being requested, in order to potentially win a contract for 20-30 or more aircraft, that could be worth around $10 Billion plus at list prices... not to mention the ability to sell more of their products, have an ongoing relationship for the next couple of decades, add to their product offering for other carriers, etc, etc, etc.
Why on earth would they bother?
It's been done before, think B747-400ER. Only 6 were ever made for Qantas to allow more reliable LAX-MEL ops. Involved an Aux fuel tank and bigger landing gear with a subsequent increase in MTOW
Did some of that development not then go into the Freighter model, which didn't sell too badly I thought?