Maybe Gray Mann since he's an engineer too right?
I don't think so...? But speaking of the Engineer, that third file the BLU Engineer had at the end of the Loose Cannon comic, it was blueprints for the life extender Gray Mann has, perhaps Gray has made a deal with that Engineer to construct all those robots for him and that's why they're BLU and whatever SFM project Valve is working on will explain all that stuff with Gray Mann, the creation of the robots, reveal what those strange Spytech models are about, and have Nolan North voice the BLU Engineer while Grant Goodeve voices the RED Engineer (or vice versa)