I admit I didn't read the thread because it's a dumpster fire.
However, I did experiment with 3D-ish graphics on the Neo-Geo a few years ago.
The Neo can do scaling in 2D reasonably well. It stores pixel data in 16x16 blocks. It builds vertical strips of those blocks, up to 16x512. It can scale the horizontal dimension from 1 to 16 pixels, and scale vertically from 1 to 512 pixels. All the graphics - backgrounds and gameplay elements alike - are made of these strips. The graphics chip is called the Line Sprite Processor Chip for this reason.
(It minifies only, not magnifies. Magnified graphics can be pre-computed and stored on the cartridge, to minify later.)
This is good enough to show billboards like the monsters in Wolfenstein 3-D. It can approximate drawing the walls... kinda. If you know you've got a span of wall to draw, you could break it into 16-pixel-wide strips, and have the Neo scale each of those. Further - you could pre-generate walls at different angles, and pick approximately the right one for the situation.
I tried processing some graphics to make this approach happen, but it didn't look very good.
I've attached the script that chops up the source graphics and the little test program I wrote to see what it would look like. Note that, really, this code has nothing to do with the Neo-Geo. It was an experiment to see, if I did write a Neo program, what it could look like. It looked like shit so I stopped.