I've played theHunter COTW on and off for a few years now, and the only thing that generally leads to me stopping playing is that I always feel like mounts are never quite what I'm looking for, and that's usually because I like whacky taxidermy. Three bears standing on each other's backs? A deer holding a rifle? Perhaps just something more normal, yet not in the game? Often when I play the game, I'll play up until I point where I find myself frustrated that I can't show off my most recent prize in the way I want to.
What I'd love, and indeed would be willing to pay the price of a full triple-A game title of, is a mount designer that integrates into the game, so that I can take my prized trophy kills, and mount them exactly how I want. Ideally with steam workshop support so that you can find interesting mounts other people have made and use them. It's obviously quite a bit of work to create a system like this. Animal skeleton manipulations, mount components, and a data sharing system so that visitors to one lodge can actually see the mounts, all that work would likely necessitate a high price tag to recoup the development hours. However, I think the creativity that the community to could produce, and the endless supply of new mounts (Any mount you can design!) would be amazing.
The question becomes partially, what would the existing mount creators work on afterwards? Mount components! Different rock formations, props, or even just continue making new official mounts that are easy for players to access without needing to maneuver through the steam workshop. Half of a mount is the available props that often go with it. Just a quick search through this channel for other suggestions results in dozens of people asking for new particular mounts. This would open up an entire new avenue for players to enjoy the game.