In the case of the armours, the meshes use a different base entirely than the Halo 4 set. The body type is closer to Halo 3's set - presumably since the game is heavily based upon the Halo 3 engine and runs the same basic skeletons.
I've figured A Thing out, though, more news as it comes.
EDIT: Oh, cool. 1111 posts. Also: if anybody ever comes to you and complains that modelling or getting models is difficult: send them to me. I'm going to use those people's backsides to shine the toecap of my boot.
EDIT 2: Sorted out my model-getting issues, files should be rolling in a bit faster now. It only took five hours and me almost wanting to hang myself.
EDIT 3: Armour Alpha pulled and textured. As always: these names are provisional and do not reflect the final name of these sets. See below for the attached image.
EDIT 4: There also appears to be a set I'm going to nickname 'Dreadnought' armour for now - it appears to be some sort of heavy upgrade to standard Gen-2 armour sets. I'm surmising that this may be some sort of field upgrade or gametype-specific set. It has no textures associated with it, and no discernible purpose at present other than appearing to be a straight armour supplement - perhaps some form of hard-light overshield. Image attached below.