I don't think that there are really any parts that you can't find for the New Edge Mustangs. A lot of replacement parts are still available from Ford. And the aftermarket is VERY strong. Also, not many Mustangs are crushed before every usable part is removed for sale on the used market.
However, some of the parts on the special edition Mustangs (Cobra/Mach/Bullitt) can be extremely difficult to find, and are only available on the used market.
The New Edge is the last generation of the "simple" Mustangs. They aren't anywhere near as as technologically "advanced" as the later cars. A damned HVAC module sure as hell won't take one off the road... It doesn't have one!