Technical factors to consider for retrofitting aerial refueling for commericial aircraft
Yes, of course this is possible.

The main factor taken into account is pilot training. Mid-air refuelling puts the receiving aircraft into an unstable position which needs to be held manually for the duration of the operation. Without proper training, the refuelling operation will carry a high risk of being unsuccessful. Mechanically the modification is simple: Add some fuel lines, valves and the standard receptacle for the Air Force boom system of refuelling (at the fuel mass needed only the boom system would make sense).

The best example is a Boeing 747-200 B which has been converted as the US presidential transport. The fuel receptacle sits ahead of the cockpit on the upper side of the aircraft's forebody. From the linked site: 


  Capable of refueling midair, Air Force One has unlimited range and can carry the President wherever he needs to travel. 




modified Boeing 747-200 being refuelled by a KC-135 (picture source)

However, this capability has never been used with any US president on board and is likely to be deleted from the next version of the plane. From Popular Mechanics:


  As part of the effort to cut costs by $1 billion, aerial refueling was cut from the program as well, as reported by Defense One earlier this month. Proponents of the cut argue that aerial refueling is not necessary considering no president has ever used the capability, not even George W. Bush who loitered over the Gulf of Mexico in Air Force One for eight hours after the 9/11 attacks. Opponents of removing mid-air refueling say that the ability to take on fuel and fly for long periods of time, even days, is vital to ensure the government can continue operating in a crisis, including nuclear war.