First of all, I question the stalling rule, as it arbitrarily bans an in-game action just because we don't like it. But I don't like it either, so I'm not going to get too picky about it.
Second, can any characters truly stall except MK, who has at least one, DMG argues two, and depending on the stage three different ways? The closest method I came up with after brainstorming with various people was Snake C-4 teching, which for the vast majority of characters could still be interrupted (if nothing else, most characters could interrupt it suicidally...) If not, banning MK (edit: plus some rule to end infinites, already in place) would cleanly ban stalling.
Third of all, a LGL doesn't actually ban planking. It punishes people for using the ledge. There are plenty of legit uses of the ledge which are not stalling, both by MK and by everyone else. You can also plank without grabbing the ledge much - you just can't do it for the whole match.