Haha, skinny Gundam returns!
Though I question it's actual use in a combat situation. It seems an awfully contrived way of defeating opponents, and would only really work one-on-one. I guess one of them is automated while the other is manually piloted, like a huge bit or funnel. A Gundam X-style drone, sort of thing.
The other, somewhat fanwanky explanation, is that since the novelisation of 00 says that Tiera would control Nadleeh via a neural interface, maybe he could manually pilot one and mind-move the other. Though that would kinda depend on whether the cockpit is physically in Seraphim or Seravee, and is a pretty awful idea anyway.
As a cool little side-note, as the Seraphim seperates you can see the GN drive sticking out of it's back. Also, apparently the booklet for the 1/144 model kit of Seravee says that it's got
another gimmick that depends on having a connection to Veda. TRIAL Mk.2? If you want to read too much into the dialogue, Tiera explicitly points out that Seraphim is different from Nadleeh, so maybe there's still a Nadleeh hidden inside Hambeast Gundam. Probably not, though. Still, the fact that it requires a connection to Veda is interesting, as it implies that either CB will retake Veda or Anew will get in the cockpit or Seravee for some reason.
Did anyone else notice that new MA has a slash harken?

. Also, it seems the wing-things of the 00 Raiser contain giant GN-cannons in them, I don't recall them being used before. Kinda bummed we
still haven't seen the GN Archer yet, even though Arios was sent out into combat in this episode with it attached. Bah!