I guess lore can always change but, this still sounds kinda crazy. In fact by doing what septim did in oblivion you would theoretically become a god or else die and turn to stone. which is why this idea still seems strange to me. Even with the power of an elderscroll.
Though what if your blood is of a different strand, by using the scroll you can uncover secrets that the Grey beards did not tell you. A secret that they did not want to tell you due to your involvement with the blades. For if you could become a dragon, then you would be hunted like one as well. So that could be a mission starter right there.
EDIT: The Martin idea was an example, though like I said. What if your blood can be utilized differently. By discovering the power of your blood through the Elder scroll you are confronted with a conflict. That in order to take the form of a dragon, you must pass the test. If you sacrifice yourself you are worthy of the ability (Akatosh being the one you try to gain favor). For you may need the ability for some conflict.