I support this idea, it is simply amazing. After playing a handful of Terraria I started thinking about Hallow alternative and a Crimson counterpart(I played since 1.1, so I always considered Corruption as a Hallow counterpart) I was thinking what is the opposite of flesh, and I'm surprised I didn't think about cybernetic organisms. This idea was explored in many games, say System Shock 2(meat vs cyborgs and robots). This counterpart is perfect.
I do have some suggestions.
I think seeds should be pointy and should be called something like "nanites", so it will suggest that nanomachines help spreading the cyber.
Backgrounds should have more cybernetic mountains, with some cyber trees, maybe mountain shapes should be geometrically correct.
Speaking about alignments in D&D setting(especially Planescape one), I think that Crimson is Chaotic Evil - the evil force that has no rules, just the spreading of the flesh. Cyber on the other hand is Lawful Neutral, it does not care about good or evil, it is the biome of order and perfection, like a precise clockwork (similar to Mechanus plane in Planescape)