I don't see why articulated plate
couldn't cover the abdomen. It isn't like a "one-torso unit" of medium plate is a single piece of rigid metal, after all. Same goes for plate gloves / gauntlets—doesn't seem to be any reason you would have to restrict it to segmented plate (although I might agree that the heavier variations of plate would probably be too thick to accommodate a sufficiently find level of articulation for fingered gauntlets. Best stick to mitts in that case).
Out of curiosity, considering how many options you offered for "plate and mail," I'm curious as to why you never used the actual
mail and plates armor option from LT.