That's an awesome idea!
I would like not just completely primitive civilizations, but also races like Earth today, with the capability of researching missile technology, and DUC, but maybe not the other guns, and with no spaceships, but with "orbital fighters" to defend the planet, weapons platforms, satellites and bases, and maybe drones...
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What about an Neutral AI that only builds units and bases?
That would make for a really tough homeworld in Proportions. I can easily see a Primitive homeworld with 300 WP, a 100 sats and a minefield of 100 large mines...., and maybe 40 000 000 infantry......