You are using acid aliens to turn any biome in desert, but I suggest create a alien biome like Starcraft goop that makes the aliens stay faster like concrete with the protagonist. So, when the aliens on the front die, those behind gain speed vantage. And this biome could be around the nest like other is around resources in my other suggestions. The art concept of H. R. Ginger could help to create this enemy biome.

I like the idea. It wouldn't be part of alien biomes but would be good as part of an alien expansion mod.