Good things come in narrow packages

[Sumpter250]

One thought........Where the actual throw bar would be on the trestle, and not the safest place for the brakeman, determine which end of the trestle would be where the brakeman would be most likely to be when the switch needed to be thrown, and put a switchstand there, with a bell crank and rod assembly, to the throw bar. That would keep him on solid ground for the coupling, uncoupling, and turnout operation.
Or.....
mount a switchmotor casting on the trestle, and a control box at each end of the trestle ( if that is era appropriate )