I'd really like to see the North American 29 be possible in COTW, in the attached photo I have Safari Club International's requirements for their NA 29 Slam. SCI has the most relaxed rules of this slam that I could find, and even so we are still 5 animals short of being able to complete the slam in-game.
That is IF you count the 4 different NA maps with moose as having shiras, western canada, alaskan, and eastern canada moose (in layton, askiy, yukon, and new england respectively.) And also if you count the layton lakes black bear as a pacific black bear, which it may well be based on region.
With current reserves there are a few animals that could be added. The Sitka deer would be a much needed addition to Yukon valley, it would fill the void of not having a class 4 animal, and add an animal to the map currently holding the lowest species count. The Wolverine could also be added to Askiy Ridge. This would leave us needing 3 more species or sub species.
For a new map I see two ways forward, either Northwest territories Canada/far north of Alaska. Or go to the yucatan peninsula of Mexico.
A map in the north could be a dual biome map similar to whiterime ridge, transitioning from mountains to ice flats. featuring the Polar Bear, Muskox, Arctic Islands/Arctic Barren Ground Caribou, Stone Sheep, Dall Sheep, Fannin Sheep, and Pacific Walrus as new additions.
A map based on the Yucatan, could feature the Coues Deer, Gray Brown Brocket Deer, and the Jaguar. Jaguars should be even harder to find than the snow leopards, with only 3 males and 3 females on a map at any given time.
These two maps and the Species they would contain, would fill in the majority of what is missing from CotW in terms of North American big game. With the only missing members being specifically localized subspecies, such as the Tiburon island mule deer, and the Tule elk.
With this could come a new achievement, the NA 29 Achievement, unlocked upon harvesting one of each of these 29 species.