Musket shooting vs melee mode neutral animations:
This is kind of a silly immersion/fun suggestion that wouldn't have any huge effect on gameplay.
I assume it is possible that muskets could have different animations depending on if they are in firing or melee modes, since weapons without bayonets turn into clubs, but my suggestion is this:
In shooting mode, have the neutral stance be as it is now (holding the musket against the shoulder) but with the addition of maintaining that stance when walking (just holding the musket at the shoulder, not supporting it with the left hand) and holding it in a similar fashion to how it was in MM when running (holding it at the shoulder supported with the left hand).
In melee mode, have the neutral stance be 'port arms': the musket is held at a ~45* angle in front of the chest, sort of in line with the crossbelts. Use this animation when walking, too. When running, the current animation is perfect.
Why I think this would be neat:
It adds a little bit of immersion, particularly for line battles: historically, the 'port' position was used for standoffs and intimidation, and prior to bayonet charges. Seeing a line advancing toward you suddenly toss their weapons into port arms and break into a run would be amazing!
In addition, it adds yet another visual aid for what mode your weapon is in. Currently, the musket icons for firing and melee are easy enough to confuse at a glance that i have seen several people accidentally speared in the back.
Anyway, I just think it would be a nice addition that might not be too horrific to implement.