So here's an idea for you. A little off the wall perhaps but here we go.
How many times when you were out railfanning/trainspotting did you sit on a roadbridge and watch trains go underneath you? Quite often, I'll warrant and even more often as a child if you were like me. How often do you get to do that on a model railway/railroad? Not very often. I can only think of two, perhaps three layouts where the principal motion of the trains is front to back. Nearly all layouts have you watching trains pass across your field of view.
OK so there are severe logistical issues here concerning the location of your storage sidings. Which has to make for issues with an exhibition manager an 8'x2' layout is easier to place than a 2'x8' one. But I in my own bloody minded way think it could be solved.
Anyway, here's a mock up to tease your brain a bit.

Having the storage sidings in front causes issues no doubt. But as I enjoy engaging the visitors in conversation (must be something to do with my accent) that wouldn't be an issue with me it could even form a part of the presentation.
Is it practical? I don't know. Its something to consider over the holiday weekend