It would be a nice feature to be able to bring out an animal from the barn/stable. (similar with the horses) and be able to lead them into a closure. It would look more realistic and give a proper feeling of life in a settlement, but also free up space in the barn/stable for breeding animals. Also some movement and animations for the animals and not entierly stationary (would be nice for the horses too, and have option to remove the tack)
One could also implement so that the animals out in the pens would eat of the grass, grass would then turn into dirt/soil and overtime it will regrow if not used. (Similar to Wurm) And one could perhaps have an option to build a feed trough to fill with better quality food to be able to raise the quality of the animals in the pen and also feed them during the winter.
If this suggestion already been made I apologize, I tried to look through the suggestions but didn't find one with the same ideas.