I agree that there should be goblinoids in the main book, preferably as a single heritage with goblin and hobgoblin as the main gifts, rather than having them as separate heritages. Bugbears are kind of separate enough from the other two that they could be a third gift, or they could be not included. I'm not sure what the fourth gift should be, though. Most of the goblinoids in D&D are just variants of these three.
(I'm suddenly thinking gift is a strange word to replace subrace--maybe use ancestry or lineage instead).
Cultures could include "City/Hive" (for goblinoids who have grown up in Gobbotopia and think of themselves as part of the whole, as Tetrasodium mentioned); "Sneaky/Shadow" (for those who have learned to sneak and steal in order to get by, possibly in other peoples' cities); "Wild" for those who live in the wild lands and lead a desperate life of hunting whatever they can while avoiding the monsters that can kill them); and "Studied" (for those who are working to perfect an aspect of their being or their understanding of a topic of knowledge--to represent the fact that in 5e, Hobs get +2 Int). Obviously, there are probably a lot more options for cultures, and the names I came up with kind of suck.
I also want there to be a generic anthro heritage, where the various gifts can represent cat-folk, dog/wolf/fox-folk, rat-folk, and one other--cattle, goat, bear, whatever.
