It is believed that people go to "Hell" to suffer from the past mistakes or be punished. Here is my idea, why don't we add "Nether Prisoners"? The mobs, which are imprisoned in the Nether such as a new type of villager mob since we have Illagers, Pillagers, Witches and so on, can change the atmosphere of the Nether. In my opinion we desperately need an update for the Nether. This dimension has a little amount of mobs in general. Maybe we can bring the Nether a new life or a new reason to go. We can even have an achievement when we "free" a prisoner mob by letting them travel through the Nether portal to the Overworld. It wouldn't seem pretty if these mobs wandered around and had no structure to live just like the Zombie Pigmen, so it would be great if there were some prison structures or "villages" for those mobs. Maybe Zombie Pigmen would guard those mobs with their golden swords and not allow them to escape and in that way Zombie Pigmen would have a purpose to live except wandering around nonsensically.
There are no limits in this update, Mojang could even add a new type of Golem or even a new boss? Current mobs of the Nether are hard to come across exception for the Zombie Pigmen. We mostly hear a sound from a Ghast but that is it. Nether is so empty and has a massive potential. My idea is adding a prison-type structure and some prisoner mobs since people mostly believe that people go to "Hell" to be punished and our mission can be freeing them or even more. We already have Update Aquatic which is for the oceans and I think it really brought life to the oceans, Village and Pillage which is in progress and focuses to the Overworld villages. It's time Mojang updated the Nether!