I definitely think it should exist, and should be in a module. It would clutter up the basic rules, but it is sorely needed. In 3e you were sort of left shaking your head. You could use the grappling rules, but then you would never succeed, because something that big could shake you off like nothing. You'll have a similar problem in Next if you make it Strength-based. You could use the climbing rules, but that didn't take into account the fact that the opponent is moving and possibly trying to shake you off.
What would make most sense to me in Next would be an opposed check where the climber gets to choose between Str and Dex, and the climbee is stuck with Dex, and must be at least 1 size category larger than the climber. In other words, exactly the opposite of the current grapple rules.
I don't see a serious problem with this suggestion, since it might be a bit easier than grappling, but you aren't taking control of your foe in any way.