Lately, I and my friends have converted many Fantasy Battle figures to join our Blood Bowl teams. We've used minotaurs, artillerists, wizards, and even 40K painboyz and a runtherd.
Big guys get strength skills only, of course.
The Carnifex may only burst the ball - he may not carry it or catch it. To throw a teammate, the carnifex must make an unmodified armour roll against them. The team doesn't gain experience in the usual way. 121-300 SPPs Team members all have two skills and so forth.