Present a uniform environment to scripts. For example fingerprinting doesn't work very well on iPhones because they are all so similar. Firefox could pretend to be some sort of "standard" machine.
That's definitely not easy but it beats blacklists which are trivial to work around.
They already do this in some areas, like returning a fixed list of installed fonts, but fixing every possibility of fingerprinting is extraordinary hard since there are so many ways to pull in some data. At some point it light actually hurt the user experience.
That's definitely not easy but it beats blacklists which are trivial to work around.