I'm well aware of that, I believe I commented on it in the original post. I don't expect my suggestions to actually be implemented, in fact, I do not expect anything significant to be done to the Great Wall implementation. These were merely my wishes.
The point was that it shouldn't block other improvements.
There would need to be some logic to determine where to draw it to make it look most visually correct. I actually don't think it would be that tricky, and not too different from how it was done in Civ 5.
Functionally it is tied to the tile.
Yeah, it wouldn't look perfect in that case, but I don't think it is that big a deal. My idea was basically to still associate the wall and any abilities to the tile, and not the edge. Putting the visuals on the edge was just how I think it would look best, and not interfere too much with other improvements or features rendered on the tile.
I never suggested that it should be. Your post seems somwhat focused on the concept of putting the wall on edges, but the "render on the edges" part of my suggestion was all about visuals.
That's mostly your idea, not mine, but it could of course be done. Features can be on edges, apparently, as rivers are a thing, but workers don't currently don't have a way of improving edges. There would need to be some extension to the UI, and I suspect more fundamental changes to the game code to make this work.