Save modpacks and mods that are in profiles in some sort of cloud. This would be first of it's kind, (as i'm aware) no other launcher has done this so far. Saving your modpacks can be extremely useful, in the case of an unexpected PC reset, New PC all together, or you simply lose your modpack. Along with that, maybe you could also cloud save your minecraft world saves. Allowing you to access them from multiple devices, and all of the reasons I stated for the modpacks. A little indicator could be shown next to the world, showing that it's saved and up to date in the cloud.
This feature could be Non-Lunar+ /or Lunar+ based on the costs of this cloud feature. You could also have limited or a smaller amount of cloud storage for Non-Lunar+ users. Or if you could some how find a way to link Lunar and some other cloud storage (like onedrive.)