I would suggest a run-around track on the inside loop. You could install a pair of switches and build a cut-off track where your drawing says "036 curves". This will allow you to push cars into some of the facing point sidings you have shown there.
Maybe you could add a passing track to the outside loop. This would allow you to hold a train on the siding while running one on the loop. When ever you felt like it, they could trade places.
