I don't think the problem is as dire as you suggest. In the first place, if there is not a shift in the formation you posted, we don't have a problem. we have 4 ineligible numbers, and at least one eligible number replacing him, so the formation is legal.
If by chance they shift from this formation and uncover one of those eligible numbers, we still have a legal formation, because the other number still fulfills the requirements put forth by the exception.
If by chance they shift both eligible numbers to eligible positions, we are still good, as long as they don't throw the ball, because nothing in the exception states that the players have to remain between the ends. The only restriction is that one of them remains ineligible.
In the event they both shift to eligible positions and one goes out for a pass, the formation and the play is still legal, because the team has fulfilled the requirements of the exception. The eligible number replacement has taken an initial position inside the ends, and because he is ineligible, has not gone out for a pass. To my knowledge, nothing prevents a player in under the numbering exception to take a position that normally would be an eligible position. He is simply ineligible because of the fact that he initially took a position between the ends.
The only problem we have is if both go out for a pass, which is really not a problem, because we automatically have a foul for illegal numbering, ineligible receiver downfield, and, should he touch the ball, illegal touching by an ineligible.