If you are okay with a script solution, you could override the _intergrate_forces function, and then only set the origin of the RigidBody2D. I have not tested it, but it would be something like this:
func _integrate_forces(state):
# I don't remember if the state transform is local or global. I assumed local
# for now, but you may need to change these to global variables.
# Store the rotation we want to keep
var current_rotation = rotation;
# Set our transform to the state's transform
transform = state.transform
# Undo rotation
rotation = current_rotation
# Set the state's transform to the current transform
state.transform = transform
