I would absolutely love to see a weapon mastery skin-earning system added for Call of the Wild. It would incentivize using the whole array of weapons and extend the gameplay.
My idea is based on the Call of Duty system, specifically MW2019.
Call of the Wild could have challenges such as, Kill X amount of animals, Kill X amount of animals with heart shots, Kill X amount of animals with iron sights, Kill X amount of animals over/under a certain distance, etc., earning camos for each type of challenge.
Once all challenges for a weapon have been completed, a premium camo is unlocked (such as Gold). If all weapons in a class are completed, an even higher tier camo is unlocked (Platinum on all handguns, for example).