here, i took some screenshots of what you wanted. the red arrow points to the Reflector/projector and the blue arrow/circle shows the alpha that is interchangeable at any times. what your asking to change is the reflector/projector.
here, your asking to remove the reflector/projector (red arrow points to it) and placing it on a different plane. the alpha that is interchangeable at any point in the day (blue arrow) is your decision on what you want it to be.
you want to remove the reflector/projector and move it onto a different plane (lets use the P38 for now)
here we have it, with its reflector/projector. you want to replace what the red arrow points to with the 190 sight (remember, using this as an example) and put the 190 sight on the P38, this doesnt work because the P38 sight sticks out at least 8 pixel inches whereas the 190 sight sticks out maybe 3 pixel inches, thus giving you a VERY tiny sight, and a historically inaccurate plane. HOWEVER, if you want to change the alpha (blue circle) on the P38 with the 190, then go nuts. its all up to you, but what your asking for in the OP isn't feasible.
(didnt know in game subscription meant anything when we were talking about gunsights
)