Treat the turntable kit as materials to build a turntable. Make the bridge from a solid piece of wood and use the plastic parts as detail overlays. The indexing needs to be a below baseboard disk on the turntable shaft and about the same diameter as the bridge. Fit seperate cams working micro switches for each direction. Sure, it's a lot of work but it should pay off in a good operating turntable.
Regards, Greg.P.