Well, apart from what Phoenix says (it indeed doesn't have shit to do with any of the original id games
), it would destroy any vertical map's flow, layout and strategical design. If you have to take a long route to get somewhere from another point, there's usually a
reason for that. If you can just hop up any time you like, you might aswell just play in a map that has no elevation, floors or sublevels. To me, that would be somewhat similar to removing all the items from a map: you remove something, and get a more generic and less diverse game. Bad? Bad. :]