RawCode , that'd make Minecraft totally stupid to play then. The mods are the reason that I play Minecraft and not of the derpy systems that Mojang creates.
And if there would be armor for horses, there should be first something like Vanilla armor for horses first.
But hell, who is going to waste iridium plates for a horse while you can fly with Gravisuite? Unless they add a Pegasus (which they'll probably also make a derpy version of compared to Mo'Creatures), I'm not wasting my precious mats for a silly derpy horse.