This looks amazing. Now we only need a mod that includes a city and quests meant for thieves and assassins.

Not sure if it fits your idea, but you could consider **Undeath **as a late game temptation for your character: https://www.nexusmods.com/skyrimspecialedition/mods/6180

Even if your character decides not to become a lich, the mod has a small-medium quest and new locations, which your character might still want to explore without completing.