My guess is that the gambeson or mantle would be unbearable in the heat and may have been mainly worn in cool weather and I would guess the lamellar cuirass (the oven) could get uncomfortable, given its name, but it was recommended for those in the front ranks. Mail has the advantage of allowing ventilation and is the least restrictive of all armour and my reading of the Byzantine manuals is that some mail was worn by practically everyone, even archers. Then there is also the horse armour of the cataphracts. And then there is the job of the horse that would have to carry all that and more on its back all day.