[Fyron]

Like research facilities, I would prefer to keep them costing only the primary resource. Also, I don't want them to be variable size with tech level (certainly not increasing), as that makes upgrading designs a hassle. I could make them cost 3200 minerals. That would both increase the build time and halve the research they make per resource...

Also, keep in mind that using them on larger bases is not really much more efficient, as you spend about the same amount of resources on Command & Control components per kiloton of base anyways.