It is not as powerful but you might be able to use this feat with dungeon master approval. http://www.wizards.com/default.asp?x=dnd/re/20031118a
This way the dungeon master does not have to worry about the creature talking or about what levels it could be trained for plus it does not take up an extra share of experience.
At your level it would have +3 hit dice, +3 natural armor, +1 strength and dexterity, 2 bonus tricks, and evasion.
If your dungeon master is really nice then he might allow the mule to turn into a dire mule and count it as being a level -3 choice.
This way the dungeon master does not have to worry about the creature talking or about what levels it could be trained for plus it does not take up an extra share of experience.
At your level it would have +3 hit dice, +3 natural armor, +1 strength and dexterity, 2 bonus tricks, and evasion.
If your dungeon master is really nice then he might allow the mule to turn into a dire mule and count it as being a level -3 choice.