Well most crpgs I've played seem to approach the issue from the opposite end, worrying that the players will be too weak for a given area. They manage by placing stronger enemies at points where the difficulty ramps up, using them to essentially serve as walls so that if the player can't beat them or can, but only barely, that's a signal for them to back off and try somewhere else first. I've honestly never encountered a game that outright caps levels by area so I don't really know how to best articulate what has been, in my experience, the norm, since it's never been an issue or something I've had to think about.
