Mine is Z by the Bitmap Brothers, 1996. No harvesters and no base building. Each map is cut into territories, and holding more of them makes your factories build faster. It looks simple, but one lost flag can turn a whole match.
It’s been on my mind because fans made a free 3D remake, OpenZ (https://playopenz.itch.io/openz), but I’m more curious about the idea itself. Why did nobody else run with it?
What game had a mechanic you still miss?
Help this person complete their AI game with that one mechanic that they are hoping will set them apart.