I think making the Front of the Body darker would already do Wonders for the Realism. It would be so awesome if we could get Remakes of all Animals from the Base Game because there's such a huge Difference to the ones from the later DLCs. Doubt though that it will happen, but hopefully if we will someday get a Sequel
Yeah, like seriously. Personal picks besides the American bison include;
West African lions = no more moss-manes....
Timber wolves = needs more ferocity in their faces, also renaming them Gray Wolf just to match with the distribution.
Grizzly bears = virtually lump of furry taters....
Indian elephants = more of a resize for this one, cuz the size difference between males and females are ridiculous.
Western chimpanzees = more variant skins with darker tinges, and less bright pink faces to add realism.