I have checked Lance Mindhiem's latest blog, and there is a picture of a model of a BW40-8 shunting in ave in Vernon CA. So Lance has been inspired enough to at least make a diorama of the location.
At this point I should outline that I am planing a number of layouts, in no particular order, this includes.
Penfield SCT yard, Glen has convinced me.
Pilbara wa not sure how this will be at the moment.
Everett Washington state, the Boeing plant.
I plan to have these layouts, and any others, have the same fiddle yard, more on that later.
However, when you take a small slice of these locations, then to model them is easy, and to a level for completion that is high in a very short period of time.
It looks like Lance has gone down this path, keeping the Downtown rail spur layout as is, he can, I guess "cheat" On this layout, with a small slice of LA. Satisfying his creative surge without effecting his current layout. I have definitely thought about the same, even a PIlbara layout in O scale (it not as crazy as you think).
So it is ok to cheat on your layout with another, I say yes.
You can even do detailed planning so that when you cheat, it won't effect the current layout. for example using the same legs and fiddle yard will cut down the build process.
Modular boards will mean your current faithful layout, can be taken down in quick time so that you can put up the "cheat" layout, with little or no consequence.
Being a detailed operator will mean that you can play more with less so this really fits the cheating concept.
A by product of your cheating is that, having spent time with another layout or modelling era etc, you start looking at the current layout in a different light, change here or there.
By focusing on another prototype or era, you can hone your skills, or develop new skills, that you didn't need with the faithful layout.
So give layout "cheating" a go, it might, broaden your horizons, develop new skills, etc after all it your hobby and you are the boss.