That's cool. It looks like your description in the boards.txt file should specify an xxx.build.variant of eightanaloginputs instead of standard. xxx is the prefix for your specific board type in the boards.txt file.
I'm not sure that eightanaloginputs is going to solve everything for you, but it might help get you going. It looks like A6 and A7 are already defined though in the standard xxx.build.variant.