Hopefully the getting rid of the Myscism class of magic results in the end of this highly inefficient way of doing it.
But if worst comes to worst and you do need to continue to search for varla stones, spend a fortune on a mage, or running around the country side looking for powerful soul possessing creatures, i think souls should be far more powerful, full black soul gems should have far more charge than any other creature.
By doing this we could make far more exciting weapon and armour enchantments. it could add a whole new realm of creativity and excitement into this already phenomenal gaming series.