So the one thing that jumps out at me is access and reach. The yard turnouts are all tucked in a corner that doesn't appear to be accessible without climbing onto or crawling under the layout. Speaking from experience reach will be an issue. Your return loops all are way too far from what would be the aisle and that will be problematic during construction and afterwards.
The other thing that I wonder about once you are framed is the stacked track on the long wall. What is the intended outcome here? This will be difficult to provide any scenic interest unless you intend this to be more of a toy like tubular layout. If your stated desire is to have tunnels and mountains there will be a great deal of hidden track, the entire blue line on the long wall will be not in view.
