Scales and feathers are formed from the same essential material - α- and β-keratins. The genes are related. Birds still have scales on their legs and feet. You are presenting a chicken and egg argument that the reason feathers exist must be due to flight, so there is no intermediate use for them and therefore nascent feathers would not find any immediate purpose. But even if you think that the relationships between scales and feathers are coincidental, you are wrong to maintain that no path exists for the development of feathers that does not necessitate flight along the way; a flight path so to speak.
Actually, that is sort of how nature works. Adapting what is at hand.
As I pointed out in my prior post, evolution is constrained. That cats and dogs have a common ancestor is consistent with evolution. That cats cannot change into dogs is consistent with evolution. That horses and dragons cannot have wings is entirely consistent with the evolutionary fact that horses belong to the superclass of tetrapods, and it is not evolutionists but YECs such as AiG who believe in dragons. It is not evolution, but rather creation that is free from constraint.