I agree. So far we have very little information on the physics/metaphysics of the Bore and the DO's prison. What is it actually made out of? What would you use to repair it?

Rand doesn't seem to have any idea, so it would make sense to use Lanfear, as she's the only one still around who actually studied it.

This is assuming, of course, that Rand means to repair the DO's prison to it's original state. He has said that he wants to kill the Dark One, which would make this point moot...