I would of thought all you need is 1 push to make buttons and one SPDT switch (the relays will do the work controling the polarity) with the SPDT in the middle of the diamond on the track diagram and the push to make on one side of the running rails, you would select either up for straight ahead or down for cross and the push to make to fire the CDU the SPDT controls the which side of the Seep motor gets the power and the direction as you can never have trains crossing from both directions you can have all 4 points throwing at the same time.
Pete