I cant see the SkyCourier being much of a interim passenger aircraft - While FedEx is a big company 100 orders in not a big amount.
I am pretty sure far more aircraft are used to move people than freight. So why basically neglect that market in this design?
As for the 747 design:-
After a downselect, Boeing, Douglas, and Lockheed were given additional study contracts for the airframe,
The nose door and raised cockpit concepts would be carried over to the design of the 747.
The 747 was conceived while air travel was increasing in the 1960s.
Boeing responded by designing the 747 so that it could be adapted easily to carry freight and remain in production even if sales of the passenger version declined.
Even before it lost the CX-HLS contract, Boeing was asked by
Juan Trippe, president of
Pan American World Airways (Pan Am), one of their most important airline customers, to build a passenger aircraft more than twice the size of the 707.
EDIT***
Experts in the 1960s predicted that the 747 would have a short lifetime as a passenger jet, eventually giving way to aircraft traveling at multiple times the speed of sound. So the 747's designers tried to future-proof the jumbo by engineering it to carrying cargo.
The main deck of the 747 was sized about 20 feet wide, to handle two standard cargo containers. To make loading easier, the nose of the cargo model of the 747 opened and pivoted upwards.
So I am pretty sure it was designed with both in mind and not as a result of freight dictations, but rather opportunities.