KDR_11k: You bring up some great points.
What do you need two screens of gameplay to do that you can't do one? I know people really don't like the idea of the map because you are thinking I want something more original...something truely special...but what is something truely special you can do with that second screen?
A map Idea is really just one single element to "How the map can be used."
Like my idea, the map would be default, but it would also allow you to get information on players (a bulletin could scroll across and you can read who is in first, and damage levels of players.)
You could click on the map and get a view of the enviroment or watch others fight. Very cool. This would also allow for larger levels with more interesting fighting enviroments. Levels won't have to be floating islands if you design the levels to have pitfalls, hidden switchs and other traps. The ability to look at a map an know what the enviroment contains and where everyone is helps you plan your attack.
Map specific attacks. These aren't just for aiming projectiles, but can be used to teleport, hide yourself from the map, disable others maps, auto teleport other players somewhere, I am sure you can think of alot more.
I would say don't look at the second screen as a map, but think of it as a user HUD that allows you to access several types of information not able to be done in a Smash Brothers Game.