The size is actually dead on perfect for a MJOLNIR armor for a non-SPARTAN. Arms must be inside and the majority of controls are macroed systems. I designed something similiar years ago. Design as in concept not Halo-esque.
This is Mark lll Spartan armor! Originally designed by Docter Hasley to fully utilize the spartan 1s capabilitys! But after only a few battles, it proved to be ineffective. So Hasley scraped the design and made the Mark lV.