House of Horrors - Quest Expansion gives you an actual "good" option for the Molag Bal quest in Skyrim. It changes the quest so that when you first go into the Abandoned House with Vigilant Tyranus you can talk him down from attacking you. The mod author is cagey about what you need to do this. It is any of these:
Speechcraft of 40
Calm spell
Amulet of Stendarr
If you don't have any of these, the quest goes as normal, and you are forced to kill him.
If you do talk him down, you immediately go into the basement and destroy the altar of Molag Bal there. Like with the Vaermina quest, you still have the option of killing him there and taking the Mace of Molag Bal. If you don't, the quest ends, and you can leave the house, and can recruit the Vigilant as a follower if you want.
I just noticed that this is a mod for SE. But it works fine on the regular version of the game, which I have.