I probably will use it, the info I managed to dig up on Gundam Wiki makes the Testament sound oddly like Exia in a 'I have swords and technology goes screwy in my presence' kinda way. In addition to that, the Testament gives me a way to integrate Shinn into the story before Kira gains the Freedom which is a necessary evil if I want to follow my original plan--I seem to have diverted from that quite thoroughly since I first started this fic.
The only problem that leaves is how to explain the 'Innovation' of Setsuna. I've thought of saying that the huge amounts of GN particles he was exposed to in Krugis were the cause, along with his (prepubescent) ten year old body, but I'm not sure if that actually makes sense...
The Testament is a prototype special operations mobile suit used by the Earth Alliance.
The Testament was originally built as ZAFT's ZGMF-X12A Testament, but was never fielded in combat by ZAFT and was acquired through unknown means by the Alliance. It is not currently known whether Testament has been modified from its original design. The Testament bears a resemblance to the ZGMF-X12 Astray Out Frame, which was built by Junk Guild technician Lowe Guele using parts from an incomplete ZGMF-X12A frame, and some have speculated that the Testament and Out Frame were built from components of the same mobile suit.
The Testament's fixed armaments consist only of 2 waist-mounted beam sabers, 2 chest-mounted CIWS guns, and a pair of Mirage Colloid Virus Spreaders, derived from those of the NMS-X07PO Gel Finieto, which allow the Testament to infect the computers of nearby mobile suits with a virus that disables their controls. This system is located in the two large horns on the Testament's head. In addition, the Testament can use the Trikeros Kai, a large shield which wraps around the right arm and mounts three claws, a beam gun, a retractable sword blade, and stores a pair of beam pistols.
The Testament can also be equipped with the AQM/E-X05 Divine Striker, a Striker Pack which serves as a high-mobility flight system similar to the Aile Striker, and is also capable of forming a giant grappling claw. The Testament can also equip the older Striker Packs designed for the GAT-X105 Strike Gundam, and is equipped with Variable Phase Shift armor and a stealth system. The stealth system's technology has not yet been revealed, but it does not involve the Mirage Colloid system used by the GAT-X207 Blitz, GAT-SO2R N Dagger N, and AMF-103A DINN RAVEN. Instead, it seems to prevent sensors from registering Testament, but has no effect on the naked eye. It is possible that this is achieved through its Mirage Colloid Virus Spreader system.