The real issue probably isn't the armor, bit and bridle. It's the combat. What you get after Awakening is a smart horse. Sure, it was trained to deal with combat, but it is still a horse, and now smart enough to overcome training. Tell me, what's keeping this horse around fighting for this big lug?
Heck, think for a minute. Do you want to ride into combat a critter that gets it's own ideas about what's best to do?