Cruiser-Feeder Concept - feasible?
The system is highly impracticable for a number of reasons.


The referred paper acknowledges that the fuel savings due to existing tankers are negligible and a new design is required. I doubt anyone is going to develop this. Even the military uses modified civil airliners for its tankers needs. Development of the tanker as outlined in the paper will cost billions of dollars and no one is going to do that for a handful of tankers.
Even if such a tanker is built, the existing aircraft will require significant modifications for in flight refueling (assuming that the tanker is standardized from day one, which is practically not possible; even the US armed forces use two different type of tankers). Basically, the structural weight goes up,which reduces performance and increases fuel consumption.
Then the pilots have to be trained for operations of both the aircraft. In flight refuelling is potentially dangerous.See http://foxtrotalpha.jalopnik.com/aerial-refueling-hooking-up-is-hard-to-do-1559495801. Nobody's going to take that risk with civil operations.
The study is extremely simplistic. modern civil aircraft fly in a number of 'flight levels', separated by set altitude. So, for refueling, either the tanker or receiver should climb or descend the difference in altitude, and that burns up more fuel.
If carrying extra fuel in the aircraft is dead weight, it makes no sense to carry it in another aircraft and pay for its operations and maintenance.
It is not correct to compare the military and civil operations. Their priorities, methods and end goals are different. What looks good on paper may not work on real life. Remember Concorde?