If you've got armor in you inventory, and you get hurt, armor should be placed on you. If you have several different types of enchantments on the same armor, AutoArmor would choose the one that best suits the reason that you received damage (fall, fire, breathing, specific mobs, etc.).
This actually is a feature/ what you can do in Mumfrey's macro/keybind mod, but it is slightly complicated to get the feature to work as you need to know how to set the macro (or script).
I dont think the part about "equipping armor that best suits the damage you take" is possible, I may be wrong but, hey, anything is possible :P