Personally, I hate when a game forces me to open a launcher to actually launch the game.
Instead, I would suggest adding modules to the actual main game menu, with news and whatever other stuff you would normally include in a launcher including options to open the Mod Menu and log menu and etc.
This is mainly because when gaming with Steam, 90% of the games you launch can be easily and simply launched via the Steam menu, and when they open a launcher it just seems unnecessary and smells too much of blatant advertisement.
However, I wouldn't remove the launcher.
It should still be available to launch either manually or through steam.
My thinking behind this, is if someone is willing to try and mod, they'd be willing to go through that extra step, whereas someone that just wants to play the game just wants to click a button and have the game launch like almost ever other game in their library.