adding led strips into the reflectors will be the way forward
have a look at these clips
it will give you an idea of what is possible
https://www.youtube.com/watch?v=J_dPoJcr...RRIrE9CDKA
https://www.youtube.com/watch?v=PjY84cwY...RRIrE9CDKA
and this is a very handy clip showing how he got the led
lights into the reflectors
pluss the reflector retro fit projector head lights he did also.
https://www.youtube.com/watch?v=H04D4erIHeI
what they have done is too fit led strips inside the reflectors
so if you wanted duel reverse lights
buy a left hand drive tail gate light unit that will have the clear lenses so both sides will be clear
then run wires from the reverse light to the other side were the fog was
this will then give you two reverse lights up top
then run the wires from the fog lights to the led reflectors
so they act as the fogs
100% this will give you error messages
mot issues maybe
but it should work
or you could make the led reflectors as extra brake lights
as many internationals have done.
by taking power from the third brake light and taking it too the led reflectors.