An interesting idea would be to inherit food groups from an foods components, that way modpack makers would only have to sort the harvestable ingredients and let the mod do the rest. possibly dump it to an file so an modmaker can tweak any balancing issues this shotgun approach might give. maybe just give foodgroups an optional modifyer in their JSON which enables hereditary of foodgroup and then at launch parses anything into that file it can find with the ingredients already there. Hope this makes sense :)

Oh and maybe an nice addition to this feature would be to be able to specify how many crafting steps it takes before something isn't considered in an foodgroup automagically anymore. by no way is this methode an perfect way for making foodgroups, but i do think this would significantly reduce the work required to make them.