Performing a (Cntrl+A/D) Step-Lean action while prone should trigger the Roll Animation the same as regular Q/E Lean does currently.
A Player using a TrackIR can eliminate the Q/E Lean binds from his control setup (they become redundant). Instead, using the Step-Lean Macro in its place (or other common actions). The downside to this configuration is that there is no way to perform a prone roll action without the Q/E lean keys bound.
Step lean should lead to a lower prone left/right stance, instead of the standard low prone right side only, IMO.
When you are fully prone .... There is no Step-Lean function. Which means the macro does nothing.
When you are fully prone ... The (standard) Lean keys (default Q/E) trigger the roll animation.
Stance Adjust Up/Down (Cntrl+W/S) raise and lower the current stance and adjust the position of the Step-Lean postures while crouched and fully standing. However, when fully prone, there is no use for the Step-Lean macro since you can't "step and lean" while in a prone posture.
If you unbind your normal Q/E Lean controls (because the player uses TrackIR instead) you lose your ability to roll while prone. Which means you must keep 2 keys bound on your keyboard dedicated solely to the prone roll animation. This is a waste of keyboard space.
Since there is no currently assigned use for the Step-Lean function while fully prone, it only makes sense to combine it with the Roll animation and amalgamate common actions into fewer key binds.
It's more efficient use of the keyboard.
With the implementation of the new left+right prone stances, this request has become obsolete.
Closing.