my suggestion would be to either to create a very slim application that works with the existing lobby or to not make a new one at all and to just improve the lobby. the goal should be to have people eventually use the lobby because it offers the most options and a place where they can interact with people. also the lobby already exists, and noone has to write from scratch :)
getting into a game quickly is imo only relevant when they want to try the game out, for the first few launches maybe - later they will want to use the lobby. a steam launcher shouldnt replace the lobby.
lobby cleanup/improvement measures could be:
- add the quickstart options to the singleplayer/multiplayer tab
- seperate tutorials and other single player missions, such that you can quickstart the tutorial, or quickstart a misson.
- improve visibilty of tabs that lead people to actual games
- launcher or welcome screen directly link to those tabs or quickstart options
- filter/menu for rooms would be useful so newbies dont get all those test hosts and other weird stuff thrown in their faces, that will reduce confusion to some extent.
