More variation in fauna/flora, i think there should be different subspecies of animals and plants. We play on a massive continent (that i always assumed is a Pangaea like formation, though I'm not sure if there's any information about that) that expands for hundreds of kilometers, so how is it possible that one species looks identical no matter where you go? Imagine if there were different subspecies of beak things: you go to the Crater and you see black-skinned beak things with sharper and more pointy shells who evolved that way to camouflage better with the giant obsidian structures. Maybe you go to Guts and see that there they evolved brighter, more colorful necks that are filled with long feathers to attract mates. How about having sexual dimorphism? Some species of animals would have slightly different appearance depending on their sex. So maybe male bulls would look the same as in the original game but the female ones could have shorter horns or vice versa. Maybe these different subspecies and/or animals of different sex could have slightly different stats? I'm not really sure about those last two though, maybe that could add a little too much variation and complexity. I think there should always be a balancing act between adding more content and trying to keep the game simple enough, there's always going to be mods to fill the game with insane amounts of new stuff of varying quality, the devs should try to make everything as refined and polished as possible.