Right now bipods are an integral part of a weapon, but if we would want to make them as an attachment, then currently in order to achieve such result one would have to:
# Add a bone to all applicable weapons that would be used as a pivot for the deployment point.
# Modify the AR logic responsible for showing the fold/unfold bipod hint.
# Add a listener to catch [Ctrl]+[C] (that's a default keybind for toggling bipod).
# Create a simple procedural animation that would move the bone down (Y axis) from the first point by the signal value.
# Create a custom component for bipods that will trigger the animation and change the signal value of the attached weapon to the defined bipod height value.
Lastly, the current implementation of bipods doesn't allow for the usage of such bipods while prone as the BaseWeaponComponent.HasBipod() cannot be modified.
The creation of such a vanilla component would make the life of modders much easier as it would allow for immediate compatibility between mods without any dependency.