Two very different suggestions based on my first two weeks in the game:
The ability to create and save “mod profiles”. I play on multiple servers, often with different mod configurations. Restarting the game every time I change my mods is an irritating but obviously necessary process, however the requirement to memorise and manually re-enter the correct mods for the correct server is more annoying and I believe potentially straightforward to address. I propose a button in the mods menu that allows you to save the currently-entered list as a profile (name chosen by the user), which can be reselected from a drop-down at a later time. That way I can pre-configure different mod settings to match my preferred servers and grab them from a simple list when I need them.
Option to hide headwear. Fairly standard request and a common issue amongst RPGs - you spend forever designing your character’s look, then immediately hide it under the first piece of animal skin that offers a defence bonus. A simple toggle to hide your helmet - WITHOUT losing the armour bonus - would allow players to express more individuality with their characters.