To further answer Stampy's question from earlier, here are some of the conversions people have done with the Chaplain mini from the Betrayal at Calth box. Most of them are simple head and hand swaps, so nothing complicated.
This last one is the most complex. Looks like the creator used some of the Tactical Marine legs from the box and some pouches and leather straps (both included in the box) to cover up the join. Other than that, it's more arm and head swaps.