Say, you want to create a ranked team game, a 3v3. You've got your team ready, you're in Team A with two partners. And say, you want to play against a team of 3 players, to be formed by a player you know - call him Andy. The thing is, you only know Andy but you don't know whom Andy wants to team with.
How do you create this game?
You enable the "ranked game" option in the settings, get done with the template, and start dragging the names of the players to the team slots. You drag Andy to Team B.
Then what? What are you gonna do with the empty slots in Team B, given that they must be reserved for Andy's friends.
One option is to leave the slots unfilled in the game creation process - Andy can let you know of his partners after the game is created, and then you can invite them by the "Invite" option on the lobby page. But ops - since you've created a 3v1 initially, it won't be a ranked game anymore.
The second option is to fill the two slots with AI's, which are to be replaced by real players after Andy gives you the names. Same problem as above: You've created a 3v3 with AI's and it's become an unranked game.
The third option is to leave the slots as open seats, and to make the prerequisites somewhat impossible to attain (like min. Level 50 player, max. 3 games completed) - so that the game is not open to public and the seats are reserved (to players that only you can invite). This would work for you. Only this would work for you, in the present state of WL.
This is a solution to the problem of ranked team games becoming unranked. I don't know how many of you encounter this problem, but for a few times I was left undecided about what to do in such cases. My previous solution was to arrange things by PM'ing to Andy, or to invite Andy to a dummy game to let him know about the plan (just in case he doesn't see the PM). But this one looks like a more efficient solution - and now you know it, too, if you didn't.
That said, the most efficient way to overcome such problems could be to add the option of "Reserved Seat" in the game creation interface.
And we need reserved seats in tournaments, too - which is something voiced in the forum many times. I don't know how the creator feels about implementing this.