If you want to be a test pilot, you need an engineering degree. The "aeronautical/aviation/airway studies/science/etc" is only useful if you want to work dispatch/operations, lower management, some industry jobs that require general aviation knowledge, some FAA jobs that require the same, and so on. Some of these jobs require heavily on other forms of experience, but the degree is helpful. Where it's not so helpful is as a pilot, there's not much reason to and most of these jobs are far more steady than pilot jobs, so when the pilot job falls through, you need a degree OTHER than aviation to pull you through. In other words, the airlines don't care (as stated above) and you're putting all your stones in one basket, and this is about the worst industry to do that in.