This suggestion is being made because pose change does not do full frame coverage. So you will have players with miqote men who would like their WoL to stand differently (the tense hands aren't that great to look at). Post change does change some of the idle animations, but you will still have many frames where your character remains with the default. A full coverage swap would be nice.
However, I would not be making this suggestion if I didn't have more to this idea. I think it could go even further to let you animation swap your run and walk cycles.
For example- au ra men have an... interesting run cycle that many players may not really like. Being able to swap it for another run cycle with a command would benefit them without upsetting players who enjoy the default run. This ability to swap walk and run cycles would play further into character customization.
As a note: the animation swaps should also play with posture. For example, with this feature you could remove the hunch from hrothgar men. Players who like the hunch would be able to keep it as well because this feature would be entirely optional.
If SE was really inclined, you could be able to swap between the gender's animations as well for emotes on top of a couple of custom swappable animations for walking and running.