Just wanted to bring this up incase Bast forgot, or maybe has as a different idea to implement later, buuuuut...
United Earth cannot build Tundra Rovers, the only human builder capable of building Synthetic Crystalline Deposits.
Or the flaw is the fact United Earth can even research the tech to allow Synthetic Crystalline to begin with.
To be totally honest, I wouldn't mind if the tech was moved FAR up the tech tree near Next-Gen energy generators, and to have United Earth build structures that can fabricate Crystalline, though at a somewhat slow rate, versus say... an equivalent building for the Zolarg, Reptilians, and/or LIS, while on a planet Crystalline is native to.