I see two possible problems with this:
Enjoyability:
-On a horse you can still move and rotate yourself via horse movement without adjusting spine angle. On foot where this isn't possible
I think it would be very annoying.
Realism:
-On foot your feet aren't locked in place like on a horse, so you can pivot fairly seamlessly. No archer is going to overextend his
spine while aiming on foot. He would pivot on his feet as he turns. If there were any penalties I think they would only make sense
during the split-second taken to reposition the feet. However, I think even this would be a fairly slight disturbance after-which
aiming is entirely normal again.
AHHH laptop battery running out. I hope I explained my position well enough and didn't misunderstand your argument. If I did
I apologize. Thanks! ^^