To those who have mentioned using this: How does it react to rubber/nitrile gloves? After checking the link in the OP, it mentions that instamorph can stick to fabrics during the pliable stage I got to thinking put on a rubber/nitrile glove (or put it on a dummy hand), put the costume glove on over that (like a basic black spandex/lycra glove) and then apply the instamorph to create the finger plating for the Halo gauntlets (mainly the knuckle and fingertip armor as seen in in Halo 4). I figure if it bonds to the fabric strongly enough, that may very well work better than trying to sew/glue plastic, fiberglass, or foam pieces to recreate the same effect, and if it's done while either wearing the glove or having it on a mannequin hand of proper proportions, that will ensure a much better fit than trying to attach it to an empty glove.
The potential complication, and the reason for my question, is that if the instamorph also bonds to rubber/nitrile gloves then you'd be stuck with having to try and peel that glove out, or else have to wear it as-is, and from experience wearing rubber/nitrile gloves on a hot day, or even for prolonged periods of time quite simply is not fun.