here's a mod to the mainline to increase train length and improve operations. the 2 independent loops make no operational sense - by creating the over/under in the upper right corner, and removing the double crossover at the lower left, the main now is a winding loop around the layout. the sidings have been improved to increase train length and to improve their usefulness when setting out cars.
the lower right area still needs some sort of small yard - the plan from reply #17 can be shoe horned into this space and nearly gives you what is needed to keep the main clear while working the yard.
-steve