Having said what I don't want it's time to say what I do. I've already mentioned the separate backscene and lighting suspended from the ceiling, so can we assume they'll be in place.
Most layouts are designed to fit a particular shape and size, the required track being juggled to fit the board followed by the scenery squeezed into whatever space is left. I'd like to take the track I want and the scenery I want, and cut the board to the shape and size this determines. There should be no awkwardly truncated buildings or dead spaces; the board footprint can be stretched to accommodate structures uncut or trimmed to avoid areas of uninterest.
I think I'd also like to break away from a deep and regular baseboard edge. There's no reason for the the framing to surround the baseboard surface. A pair of spars running along the major axis could sprout tapered outriggers that would reach to the edge. I'd be tempted to reduce the leg structure to a single, stable, heavy tube that would allow the under board support to be lost in heavy shadows from the overhead lighting. Hopefully the sketch shows the relationship of all these parts.
Mind you looking at it something troubles me. There's a hint of loft living, Cafe Nero or DFS about the whole thing. None of the above are to my taste; I'd like to inject a more homespun look yet keep the principles, have some fun without it coming across as theme pub. I'm not sure if this will be possible. Perhaps it's time to concentrate on the layout and see if it suggests any ideas.