Having the ability to change the rendering order and customizable FOV for certain objects is an important thing to have when creating first-person games.
For example, many first-person shooters render the weapon in front of the scene to prevent the weapon from clipping with world geometry. Also, when the FOV is changed, the weapon typically keeps the normal FOV so that it doesn’t stretch. A system like this is not currently in Unreal Engine 4, forcing developers to come up with workarounds such as scaling the first-person weapon model down, which comes with the caveat that it can mess with the lighting. Being an engine that was built around first-person shooters and is commonly used to make first-person games, this is a feature that would be really useful for Unreal Engine developers.
A good system would be to create render layers with different priorities and assign actors to the render layers, making it easy to change the order in which the game is rendered. A similar system could be created to handle layers with different FOVs. I am not sure how Unreal Engine’s current rendering system works, so I am not familiar with the complications that may come with creating a system like this, but if possible, this would be a very useful feature to add to Unreal Engine 4 or Unreal Engine 5.