A valve that a groundperson could reach would be (have to be?) positioned within reach on the engine or pylon. By the time QF32 was on the ground, danger of in flight fire was by definition not possible. The fuel leak was at the forward spar near the Fuselage, and interior the wing. At best, #1 could be stopped with such a provision, but we know through unfortunate circumstance (TooLoose) that run on is relatively safe. Fuel fire was avoided by QF32 by mere chance, mid air, one of many fortunate blessings. One could even argue that because #1 ran on, fuel was removed from the penetration area of the wing, perhaps forestalling a mid air fire. IMO.