Here's an idea for a mod, if it's even possible.

Floating Alien Structures (the floating towers you see on Frigid Biomes) give you Geothermal resources if you work them after completing their related Marvel quest.

However, Abandoned Alien Cities (in the Arid Biomes) do not give bonuses. Neither Ancient Alien Metropolises (Arid), nor Ancient Alien Structures (Frigid) give bonuses, either.

But what if someone made a mod that gave these alien constructs gave bonuses just as Floating Alien Structures do, if you engulf them in your territory and work the tiles they're on?

I was disappointed when I built a city next to a Ancient Alien Structure in the North Pole on the Frigid Biome I was playing on, only to find that I didn't get any cool bonus for settling near it and buying the tiles it was sitting on.

I really liked the idea of appropriating ancient alien technology or reusing it in my game, which is what I did on the Frigid Biome when I completed the Marvel quest which made Floating Alien Structures useful to me. It's sort of immersion breaking when you can't make use of a giant alien city or structure once you own its tile.

Perhaps bonuses can be applied to the Colossal Alien Fungus as well.