Steam Family Sharing left beta today, it is a system which allows you to share the games associated with your account with up to 10 people on up to 10 machines. For more info you should check http://store.steampowered.com/sharing/
So if the 4 DMF steam accounts can be recovered, we should probably set them up to share with each machine. Then when singleplayer games are bought/added to the accounts, each account will gain access (and rotate through so hopefully each account has a good selection even when all libraries are in use).