I think the key, is the difference between being disqualified and being banned.

If you are merely disqualified, then you are allowed to take another test and then can drive on the road again, I would imagine at that point if you took a foreign test then you'd be ok, but if you are banned, then you are banned, its not about wether you have a qualification or not, its about the fact that you are banned from being on the road.

So I would imagine once the ban period is over and he needs to take a new test, he could potentially at that point do a foreign one instead if he is looking for a reason to pay higher insurance premiums or something like that.