Ok, so you could have just clarified that when you said "In Battle Class switch" you really meant to say "Out of Battle Class switch". That I wouldn't have had a problem with, as it was really the "in battle" part that made it untenable. (Or perhaps you're the one who should have gone back and read your own post again.)
They could allow switching classes in duties with the same restrictions as doing so in the open world (out of battle only, and with the same skill cooldowns) plus the additional restrictions of remaining in the same role and at a level (or iLvl) that's permitted in that duty.
