I looked through the descriptions of most of the armor and two specifically jumped out, the Cypher and Void Dancer armors. Both are really cool sets but the little lore tid bits intrigue me the most. Here are the descriptions.
Cypher
Helmet-CYPHER is not the most mysterious of the Io Design Lab’s many products, nor is it even the most secret.
Armor-Supposedly a pilot program, industrial espionage revealed the CYPHER actually entered mass production in early 2557. This discrepancy has prompted ONI to begin probing IMC’s shadowy Io Design Lab.
Void Dancer
Helmet-The VOID DANCER does not meet all Mjolnir standards, sacrificing compatibility so that Emerson Tactical Systems can integrate its own black-box components.
Armor-The VOID DANCER answers many tactical questions for the UNSC special forces community, but its unique design features has raised alarms in ONI.
Both of these have one thing in common- the armors and companies are getting the negative attention of ONI. What could either of these armors have that even ONI would be worried about? Personally I have ruled out Forerunner or Ancient Human tech since we have our fair share of those armors and neither of these seem to be inspired by either designs. The Void Dancer does mention “black box components” but I highly doubt they are referring to the sarcastic (and amazing) AI Black Box. According to Wikipedia the term is common use in cybernetics and programming referring to an object that can be viewed by its inputs and outputs without knowledge of its internals. Cypher seems a bit more shady. So apparently Imbrium Machine Complex has a secret research lab that produces many secretive technologies including the Cypher armor that was hidden as an actual armor system until ONI sabotaged IMC. The fact that the armor reached mass production while still being a secret means that there is something IMC didn’t want people to know and that they wanted to use it on a large scale. Now a Cipher by definition is an algorithm for encrypting and decrypting. If the armor had been in mass production around 2553 I would have put my money on it being armor for the 300 some Spartan IIIs working for ONI but the description states 2557 so it’s probably less likely. Also probably an unintentional Easter egg, but in Metal Gear Solid, Cypher is the name of a shadow organization trying to control world events through espionage. Any thoughts on this? I’m definitely looking too much into this but I want to see others ideas on it.