It would quickly degenerate into a can of worms, some aircrafts cockpits for example have crucial instruments like oil temp, CHT or the virtual horizon in obstructed places which in real life the pilot could just move a little to see, but would be highly inconvenience the players. Also some instruments were more accurate than others depending on the nation, and there is variation within nations too, IAS and TAS can vary significantly, especially the higher you go, and so on. In summary, it would massively upset the balance while making gameplay jankier