There is no way out of it; you have to fly the "dummy dates" to get INVOL; this would allow an extra segment or routing that otherwise violates the rules. But once you change the date, it requires reissue which then causes a routing check and you lose the INVOL benefit. You can try arguing the case that the INVOL routing change causes you to also change the date for some related reason (visa for transit, elongated travel time interferes with plan, etc.) but it is a very long shot. However a sympathetic agent/supervisor can "buy" your explanation if they want to and authorize INVOL with date change, but it takes more authority than the average agent has and they need some documented reason.