implement a multi block structure able to rotate trains to different tracks.

needs some sort of power input (HV?)
needs a smart mechanism to line up track properly? (make it so you build the track as part of the block then you connect to the blocks track)

Much like most turntables, perhaps it could be done in Minecraft by "locking" the unit(s) to be rotated by the coupler system, which then would also unlock the turntable for movement. Then via a gui, (a circle with labels going off it for tracks and "stop" numbers), select where the table should turn. Perhaps include two buttons to go 360 and 180 degrees.

I would like to add Transfer tables to this

Shouldn't be too hard its a turntable without the turn.