Like the title says, the user will be able to change the fixes defines in their own code, like when using the neoGPS with PlatformIO "lib_deps" option.
Can't you just #include <GPSfix_cfg.h> at the top for the include-guard and then just #undef things? You can already just #define things above the first NeoGPS include.
Like the title says, the user will be able to change the fixes defines in their own code, like when using the neoGPS with PlatformIO "lib_deps" option.