Some ideas that could improve the experience in my opinnion

A page similar to steam workshop with mods. Mods could be added from different sources, similar to how the download sources work but most importantly, the ability to download files from the steam workshop would be the ultimate achievement. Having a built in mod managger that could auto update mods and other addons would be a huge step forward to really bring the experinece close to as if the user actually owned the game.

Plugin support with a webstore similar to how the appearance settings work.

Ingame overlay similar to steam’s

Probably an own patching method that could replace the need for running steam if you want to play online cracked

A whole library page, not just a list on the left, and the ability to choose which page to load to when starting the launcher