I think it would be a nice added feature if being encumbered had an effect on your combat prowess, could be something as simple as having a negative AB effect to go along with the reduced speed, remove dex bonuses to AC, add a chance for arcane spell failure, an encumbered mage might not be able to get that somatic portion of thier spell just right and fizzle. Then maybe give Oxen a few more hitpoints to alleviate the situation a bit.
Just another random thought.
Vyris
