The new stance-modifier to switch the stances in combination with WSAD is not useful while moving.
I would rather like to see the ability to change the stance by moving the mouse and not using WSAD, i.e. press and hold a defined button and movin the mouse in the direction you want to *fluidly* change the stance (Up->stance up, Down->stance down, left->peek-left,...). After the key is released, the character is fixed in that stance until you stand up, crouch,etc. with the normal buttons.

Pro:
+You can adjust stance while moving in any direction
+Adjust stance on the fly, not like "Which stance do i need now?, ok, setting up, moving into position"
+Soldier movement is more fluidly between stances *and* in movement and not robot-like divided into different stance-steps.

Contra:
-Aiming at an enemy is limited as long as the key for stance-change is pressed. Has to be released to aim.