I'm completely with goldfish and vdvsx on this one. If you like the command line you won't have a problem learning a few extra commands to install thngs. If you don't, and don't want to learn, all it's going to do is provide confusion.
"I installed mplayer but can't find it in the menu."
I think having an extras-cli repository would be a mistake because it would get enabled in order to install things like mplayer as a canola/kmplayer dependancy, and then we'd have exactly the same problem again.