I don't think what and where the obstructions are in the room is really an issue. He has the use of one corner. 9' along one wall, 5' along a second wall, and due to some obstruction, it appears he won't have access to 3' of the 9' length on the other side of the layout. That means, he will need to have at least two removable access panels on the layout. He will only have access to the layout on two sides. Along the 5' length of one end, and 6' of the 9' length of one side.
With the requirement of one line that could operate in a loop, a shelf layout is pretty much ruled out.
You are making a few unstated assumptions there, Jim.
For one thing, you seemingly assume that the layout will be operated from somewhere below in the lower left hand corner of the layout, and that access to tracks in the interior will be infrequent, by way of removable access panels.
Another way of using the same space would be e.g to make a biggish (like 6 feet x 30") operator pit in the center of the layout, and operate it from within the layout. With a lift out, lift-up, swing gate or duckunder to get into the pit.
Or making an U-shaped layout with a removable plank across the entrance for continuous running in a loop.
Or substitute pendulum running instead of loop running for continuous run in display mode.
Or going from H0 scale to N scale, so it would be possible to do a turnback curve with a not too sharp radius in 30" of depth.
Or maybe it would be possible to do something around that corner jutting out into the room, 3 feet to the left of the lower right hand corner, so one could have a dogbone shaped layout walk-in-layout.
And quite possibly other things. But to understand which limits are absolute and which
might be negotiable, it would be helpful if Timo took take part in the discussion, instead of just answering questions perfunctory.
smile,
Stein