Hi Paul
You had already thought about adding a loop and wires at Edge Lane so I don't see the problem in adding an overbridge between Pighue Lane and Exhibition as a scenic break, it's the only one your short of!! And if you still want wires then assume the original plans to electrify between Liverpool and Earlestown had been completed and that the section between Exhibition and Olive Mount was done too, more plausible than a stabling point on the Bootle branch. There were actually electric holding sidings at Exhibition anyway.
Regards
Mike