Switching from lower to higher poses or vice versa has a noticable delay. It would be much more practical and natural if you could control the up and down movement with the mouse, instead of it being fixed to certain heights. That way you could move up behind cover in a much more gradual, immersive and less obvious way.
For example: Instead of pressing ctrl+W to move slightly up, you simply hold control and move your mouse up, and your character would move along with the movement of your mouse, disabling your aim as you move, but giving you more control, safety and also the ability to pull back down quickly and instinctively in case of incoming enemy fire. Resuming movement would then switch the gradually-defined pose to the 'nearest' predefined pose.
This could work in addition to the current system instead of completely replacing it.
An final example of how it could feel(in the current gameplay) is when players lean to the side before strafing around a corner from a small distance to slowly scan what's behind it, while revealing as little of their body as possible.