Thank you @hellxpress. LaunchBox is admittedly more focused on the launcher aspects, but obviously cataloging and databasing is also an import aspect of it. We are looking at adding additional scrapers. First off, MobyGames is working with us to create an API that we can use; I'm hoping that happens relatively soon. In the future we'll look at others as well.
I do have automatic adding of ROMs and stuff on the list, but I don't think I have that for Steam. Feel free to add a ticket for it here: https://bitbucket.org/jasondavidcarr/launchbox
For duplicates, this is admittedly something that needs improved in a number of ways. You can use versions, or you can use one game and add additional applications to launch multiple versions, but there's currently no way to associate two games together.