So I ended up starting to write something pretty long for this. At first I couldn't think of any Oblivion waifus, then I just happened to be doing this quest in-game at the time and things developed from there.
Faustina, leader of the Sirens. Starting with an alternate quest ending for that quest. With high enough speech and (any combat) skill, you can get her disposition high enough and then intimidate her into a resolution which involved her and the girls going to jail. After all no one's been killed yet. Like a combination of tactics:
>Like you said, no blood's been spilled yet.
>Are you really willing to have this weight on your conscience?
>You said the guardsmen must have been dumber than you thought to send me here alone, but it sounds like they've been a step ahead of you for a while now
>I think you can guess by now that they knew they risked nothing sending me here alone
>Your life doesn't have to end this way
>Drop your weapons now and you won't be hurt
>etc
>she agrees, the guard couple bursts in and arrests them
>the other two just sit in jail and sulk and curse at you if you come, so does she at first
Then the hook for another quest:
>elapse several in-game months, she will become willing to talk to the player if he comes to visit her
>elapse more time, if he hasn't visited in a few years game time she will send a cold formal letter asking to see him, then express attraction and beg to be released, having seen error of ways
>alternately, if you visit her before that and do a bunch of talking and persuasion she'll "come around"
>either way, thereafter you can go to [authority figure] and ask for her to be released
>must have even higher speech than before to get them to consider it
>"Even with the Hero of Kvatch vouching for her, she's still done terrible things to the people of Anvil. We know how close she came to trying to kill you, and we know she was willing to kill anyone who put up too much of a fight or talked to the guards all along. Hell, she threatened [that male guard plant] enough before letting him go."
>end up managing a trial for resentencing, you actually have to show up in the prophet's hangout across from the temple at the proper time and answer the concerns and accusations of members of Anvil, and plead to each of the jurors (through dialogue, but with more options to convince more of them if you've raised their dispositions previously)
>manage to work out a deal whereby you can do "good deeds" for the affected people and families as well as general good for Anvil in order to "pay off her sentence"
>jurors acknowledge this is manipulative of them to do to hero of kvatch and cautions him that it's far, far more manipulative of Faustina to let this go on, and that they don't think Faustina has changed one whit
So now you have essentially a Faction quest only instead of membership you just get one waifu who was going to kill you anyways. Talking to members of the city guard has you send them to various people's houses in the community to clear out attic rats, act as counseler for marital problems (with real NPC relationship consequences and maybe even ways to fail the questline altogether if you don't have high enough speech to pull off a lie to the guards like "they were better off separating"), retrieve long-stolen-and-pawned family heirlooms (like in the original quest but not fake), help get businesses running well again to provide coin for broken families, so on, so on. Then eventually some good old-fashioned "go to cave, kill beast threatening town" sorts of things. Kill x # of bandits hanging around on the roads in the region. Raid and destroy specific band of bandits more evil than the Sirens were could be the final quest.
This entire time, Faustina is being the sweetest most repentant little thing, saying how she doesn't deserve it and she can never make it right and doesn't know if she can show her face in Anvil even to walk to the gates, and she's so sorry and player is so noble and she'll try to be worthy of his love…then, after getting out, she travels with you away because she says she can't stand to stay in Anvil where she's hurt everyone, has you take her to an inn and get a room (uh oh, we might be getting 2 mature 4 Bethesda here :^) ), and you go to sleep…to wake up with all of the gold you were carrying gone as well as any enchanted items.
Here the redemption questline ends and is replaced with a similarly epic "Taming of the Shrew" saga.