I actually liked the idea of them using intellect mail. and you don't need something clunky like forgetting to use plate. all paladins can use both mail and plate, even Holy, but holy paladins get the bonuses they get from Plate (5% int, bonus armor) from using mail. transmog can be handled by the eventual loosening of transmog requirements, which blizzard said they could do. It's pretty possible that they will allow armor type A to be mogged to armor type B.
retired tank, holy power killed it for me.