Some stuff that can be added into this

[progCan]

Not much to say, it's in the title, so here is a list of some ideas:
-Multiplayer features
-Downloading source ports directly from the launcher (popular ones like Chocolate Doom, Crispy Doom, GZDoom, PrBoom+, DOOM Retro, etc.)
-Relative file paths for portability, e.g. being able to create an "IWADs" folder in the folder that the exe (or any other file depending on the OS) is located in and just saying "IWADs/example.wad" to the wad path so that the setup works no matter where the launcher is in, this is especially useful for running doom off of a usb. Doom Runner also does this.

[nstlaurent]

Doom Launcher by default is portable. Everything is stored in the GameFiles directory.