Hi, Keith,
Many of the pumps I have taken apart show evidence that the impeller was balanced during manufacture. There are often some (I've seen 1 to 3) shallow holes drilled in the impeller which clearly were done so the impeller would spin smoothly by having its mass uniformly distributed about the center. (Like balancing a wheel on your car.) I would not use one with a broken vane, but I would think it reasonable to break off the opposite vane to keep the balance. That will impact the flow rate through the pump; I can't say whether it would be enough to starve the system of fuel. If you try this, let us know the result.
Joe