Well shoot, I may have a decision made. Called a local sign shop and they have 3mm and 6mm foam PVC scraps. Asked for a price and the owner gave me a similar price to what I’m seeing online. Said she had various thickness 3mm, 6mm and a few others.
But, NOW you have an excuse to attempt the alternative! 
(Shouldn’t scraps be REALLY cheap?)
You got lucky. My boss refuses to sell “drops” or full sheets to people. Employees are allowed to take anything under 2 sq. ft. that would otherwise go in the dumpster. Larger drops are held for small jobs. I can usually talk him into some larger pieces when I have a need. I used to horde the stuff, but stopped bringing it home when my garage got full. I used to haul a lot of PVC and Acrylic scraps to meets to give away, but not recently.
I’ve done scribed siding for a box car, wasn’t too bad, but bricks. I don’t have the patience, even with that neat trick for doing the horizontals. I still haven’t figured out how I am going to do this one - my DNF from the MIK years ago…
The owner I talked to once I explained what I wanted and why said “how much do you think you need and what are you thinking price wise.” That blew me away. She said she uses the scraps as well but we could probably work something out. Worse case, I go to TAP plastics across Puget Sound and get some from them. I do have a small sheet that Cliff sent me that I need to try out before I commit fully.
Forgot to add that Sintra is once again ONLY a brand name and I hope this helps with the strive for accuracy.
Foamed PVC is the term I used when called. Yes Sintra is a brand name like Kleenex. 
Cut your panels and draw out the the lines with a ballpoint pen. PVC board is VERY forgiving and quite rewarding to work with.
Over thought is your enemy! But you don’t have to ask me personally how I know that?
Craig, Am I missing something, with all this talk of guessing measurements? From the picture you posted I would guess the building is still standing, why not just go measure it?
Rick,
Yes it’s still standing. It’s just on the other side of the “pond” from me. I know the overall building footprint already but am trying to figure out the height.
That would certainly be the easiest and if I made a trip over to Redmond I certainly would be a tape measure and go from there.
Getting back to your prototype. I just took a look at the Google street view (which is excellent) and I notice that the brickwork is on multiple levels. This is going to require multiple wall thicknesses. It would be helpful to know, where the horizontal courses are climbing out from the windows, how deep each step is. In 1:29 the thinnest PVC board (3mm) is close to 4" (looking at my scale ruler, not doing the math). That might be too thick for those steps.
Are you willing to deviate? Probably not 
Jon,
That’s part of the reason I’m drawing it in CAD to figure out those steps. If my math is right 3mm equals 3.4" which is darn close to my thought of a 3.5 x 3.5 x 7.5 brick.
This stepping is what is making me think 3d printing it might be the best option. I probably could get the columns in one print, and then the horizontal runs better the columns in another.
The huge blank wall with only one window would be the challenge to print and glue together.
Unless those bricks are something special, and they don’t seem to be at a casual look they are standard bricks. 2.5 by 4+ by 8-8 1/2 inches.
According to this website the standard size is 3 5/8" x 2 1/4" x 7 5/8" with a mortar thickness of 3/8".
Regardless, it’s pretty easy to adjust the brick size and mortar spacing in the CAD.
I put out a request on Facebook to a Redmond group and I’ve possibly have someone willing to measure some bricks for me on Thursday. 
https://www.bigrentz.com/blog/brick-dimensions
So I played around some more with things, and mocked up the biggest, blank wall (well it needs 3 windows) based on my max 3D print size. I would need 24 prints to build up the entire wall. That’s assuming I can glue the walls back to back without a gap. If I went this route, I’d have to glue these to a styrene core.
I guess next step if I want to take this route is to print a couple of sections, glue and calculate costs of the resin. Well and see what it looks like.
I’d need approximately 8 sq ft of either resin or Sintra. If 4 sq ft is $25, than that puts a Sintra building cost around $50 +/- a few other square feet.
Resin is about $1 an ounce give or take. My slicer program is saying it would cost me $.75 per sheet. So the entire wall would be ~ $18.
Total approximate cost for a resin building would be $72 give or take. Basically about the same cost. Resin would definitely have a time saving over hand carving.
Printing IS a lot easier than carving…
but you would have figured that out about 5 minutes into carving!
So have you decided???
Don’t know yet. Part of me wants to carve just to say I did…
Well, if you are REALLY into tedious, carving is GREAT!
Self torture began a long time ago when I decided to start prototype modeling. Trust me there are days that I wonder why I call this a fun hobby.
I say carve away!