Yawn.....
Tintin, my given ATC example highlighted the futility of good ideas in Qatar, and was related to ATC airspace management not airline fuel economy; however having said that, speed control will also save an airline fuel and for that reason I entertained your simple question with a simple answer. And although you will probably always remain ignorant, the truth remains for others to see.
Yes a Cost Index zero descent will save fuel, about 40-50kg compared to Cost Index 30. However, every A320 holding pattern will cost an airline approximately 300kg. Given the previously stated problems at Doha Radar, an agreement between ATC and the Goat that will reduce ATC workload, improve efficiency and increase the achieved landing rate would save much more. And enhance safety? Is this too difficult for you to imagine Tintin?
Note: Professor Tintin will now say he rarely gets a pattern in Doha. True, he gets vectored for 30 miles instead. This point highlights the problem. With only one controller available, holding patterns are difficult to manage. Vectoring the indians in a wide arc around the wagons is easier to manage visually by a lone controller.