You will need at least four uncouplers unless you change to delayed action couplings.
If you can curve, or rotate the whole design, so that the end of the headshunt is at or nearly at right angles to the end of the baseboard, you could extend your track to off scene cassettes, small fiddle yard or another scenic section at a later date.
Looking interesting whith some nice space between the sidings for vehicle access and possible a small goods shed / provender store.
Gordon A
Bristol