I'm okay with a lift bridge entrance or duck under for access to the interior of a walk through plan somewhere along the bottom of the green area.
That's going to get old as you get older trust me. You may want to rethink that.
I hear you. I'm not thrilled about the idea either, but not sure how else I may be able to squeeze in a two track mainline around the perimeter if the table top of the surround is only 30-36 inches from the wall. That pretty much rules out anything like a dog bone or double ended loop. But I understand what you're saying and I am committed to nothing at this time other than to a) build something b) what I'd like to model (Strasburg) and c) the accessories I have that I would like to feature. Thank you for the spot on thought for consideration it's greatly appreciated!