We've done this to death in the past, but my biggest concern is that the reflective plate on the back improves visibility massively in the dark.
A Morgan with non reflective plates and two tiny round red lights set low down is lost amongst traffic on busy motorways in the dark. I followed one once on the M42 and it was almost invisible.
Dave,
I agree. It is like removing the 3rd brake light. I get the "look" idea but anything that stops the brain dead from seeing my low dark car is worth it.
If you like old plates why not add them at rallies etc.
John