DISCLAIMER: I have not seen your layout and have no concept of what you have accomplished. I am certain that you have a very nice layout, but there are some things that I think about that I don't believe the average 3 rail modeler considers when building their layout.
I was in HO for a number of years until the eyes started having trouble reading reporting marks. I also did not have room for the smooth radius and transitions of O scale 2 rail modeling. But I felt I could live with the truck mounted couplers and the O-72 track available. Thus the move to 3 rail.
I attacked O-72 3rail much as I attacked HO scale...if it is not important to the operation of the railroad (such as fuel/sand/water) and was not a shipping or receiving (or both) customer, then I did not have the space, time or skill to waste on building "scenery buildings". What I wanted/needed was industries that would ship or receive via rail. Would I have liked to have had room for Main Street with drug store, department store, ladies ready to wear, appliances, town hall, church and maybe a couple of gas stations and 15 houses, PLUS the railroad "customers"??? You betcha! But I did not have the room for the "wasted space" for the houses 2 blocks from the railroad...or the volunteer fire department (which I wish I could include).
I neglected to mention that I am doing my 3 Rail O-72 railroad on the exact same benchwork that I used for HO. So space is an absolute minimum and everything has to fit. The railroad is in a free standing "storage" building in the backyard.
My influences have always been "project railroads" by the HO hobby press. After getting over the shock of 3rail when I first bought it, I also realized and got over the shock that I have slightly more than the equivalent of an HO layout measuring 4ft by 8ft with an extra shelf...which compares fairly accurately to my "around the wall 19ft by 15ft with a 4ft by 10ft peninsula 3 Rail O-72 layout". So, if I felt I did not have room for houses and grocery and hotel in HO, I promise I never even blinked in 3Rail.
The HO hobby press talks a lot about "selective compression" on the entire layout including industry size, train size and the "must have" structures. So...
My switching zones have to fit along one wall...every wall stands alone in this aspect...and the two sides of the peninsula operate independent of each other. So using a sharp knife, let's dissect my Oklahoma City Stockyards Switching District (sorry, but most of it exists in my mind, so NO photos).
On the two long walls, I have to allow for the track continuing beyond that shelf. (true of every one of the four room corners and the peninsula, right?) Thus I need to make a 90 degree turn. For simplicity, we will look at the wall in front of the computer and imagine it to be my layout shelf/benchwork.
I am using O-72. I need a 90 degree turn on the left end of the wall and the right end of the wall. HALF of a 72 inch diameter circle (two 90 degree sections) are a total of 6 feet. Take that off the 19 feet shelf and I am down to 13 feet. Take off enough for a turnout/switch at each end of the corner curves. Without going out to the train building at this hour, let us just assume that a switch is "roughly" 1.5 feet long from inside the pass track clearance points and the same clearance points for the main line; times two for two switches (1.5 x 2 = 3ft), one on each end of that main and runaround track...so now my 13 feet is down to only 10 feet. Locomotive and caboose are about 2.5 feet. We are now down to about 7.5 feet.
NO cosmetic curves, I use straight track to save space. But the problem is...I have to leave room on both ends of the 19 foot shelf for auxiliary tracks. What tracks? Well on the end without the peninsula, I have an industry between the main track and the wall on that shelf. On the wall with the peninsula joining the "around the wall shelf"...my "Staging" hides behind a view block and thus requires about 10 inches more or less for a single train stage track off the total available for the model railroad main line. So, just rounding it off....locomotive (4 axle geep, six 40 feet boxcars and a traditional offset Santa Fe style caboose.
I am down to a short train and I have not included a single industry or house or retail or warehouse of fuel depot. There is no room for houses and scenery will be an absolute minimum to fit the available space.
Plan your operation. Visualize the amount of space you require. Take a little extra room for safety.
As for where to find "Fat Tony's Wholesale Market"...metal prefab or brick? Nearly any warehouse would work in nearly any and all circumstances.
I am sure that if you check out the websites of the "usual suspects": Ameri-Towne, Korber, DPM, Lionel, MTH, Menard's, Model Structures and several OGR forum custom builders...you will find a large handful of "Custom Designed and Assembled" model buildings such as the great new "XYZ Warehouse" or the "ABC Manufacturing" that will fit your exact circumstances.
But stash all the current surplus buildings. In 2 years, if you don't put any back on the layout, you didn't need them the first time around. Find a model train club and donate...or build a "play" layout leaving some of the old buildings from the current layout on the table for the grandkids to enjoy.
Did that cover what your point was....no room for customers and shippers and receiving customers due to all the retail and industrial and commercial building that are on Main Street and not facing away from the track with the loading door at the loading dock at "Main Street".