What if Zenimax added a new NPC guild that was the polar opposite of the Thieves Guild and Dark Brotherhood? This guild, called the “Justice Guild,” would be the lawful good guys that protect the citizens of Tamriel and uphold the law. Not everyone wants to play a criminal! This is a perfect addition alongside the Justice System, which is also in development. There will be no PvP combat within the SAME FACTION, but a chase mechanic will be added where the thief must outrun the justice officer. If the justice officer gets close enough to the thief as they are committing a crime, they can use their “handcuff skill” that’s associated with their skill tree. As soon as a thief is caught, they are put in jail and a dialogue box pops up for the justice officer with a gold reward. The justice officers (players) will be an addition to city guards (NPC’s) to upholding the law. Furthermore, the thief will also have skills, such as “evasion” to help them outrun the justice officer. It is pure running madness, one trying to escape, and one trying to capture. Basically in a nutshell, it would be...

Justice Guild + City Guards <----------> Thieves Guild + Dark Brotherhood

(Good Guys) (Bad Guys)

Interesting, sounds a bit like the Stendarr people or whatever they're called.

No the vigilants of stendaar are against dark forces like witches, vampires, lycanthropes, and daedra. I think the op is talking about a guild or faction that focuses on thieves and law breakers.

Can we call them the Justice league....

Yes

If there was a simple diagramm to show what TES is not about, this would be it.

Hah. Well, while I agree that it should not be thought of by any means as "good guys" vs "bad guys", I don't think this should be ruled out. For instance, you could have the justice guild in the employ of the major trading companies in the three alliances. We know their own motives are often selfish and corrupt, but they still profit from maintaining law and order and suppressing anarchic elements that can cut into their profits.

Course, this also introduces a PvP element in the non-Cyrodiil areas, so I don't see it happening.

Though you could have a similar organization whose targets would be NPC criminals rather than players.

What if this worked both ways the NPCs act as resources, by targeting NPCs you lose resources, and funding limiting your ability to operate in an area like exposing fences or bribed officials thieves are more exposed in these areas, likewise bribing officials and planting incriminating evidence would make thieves sneakier and Justice guild members less trusting, thus making officials less likely to crack down on a group or area. Or something like that.