My 4/4, being of 1986 vintage, didn't have a high=level brake light, but rather than fitting one where luggage might obscure it, I fitted an LED strip to the lower rail of the luggage rack, so that it's visible whether or not one is carrying luggage.
It's still above the level of the standard brake lights, and people who have followed me report that it's very effective.
i've been thinking of the same thing myself.
