Coincidentally, my Journey of the Lone Wolf thread now has a WIP version of a mod that makes it so that only one Source Hunter shows up in the Main Campaign (no guarantees on whether the game is completable though).
This thread showed up around the same time that I was experimenting with the idea and had posted my thread on it. I didn't have an actual mod working at that time though. But now I do, and there haven't been any obvious issues so far.