Only those of Ishgardian origin can become dragons after drinking of dragon blood (and a specifically prepared dragon blood, mind you), because only them descended from one of the Knights Twelve (they gained this ability, and thus all their descendents, because they gouged on Ratatoskr's eyes). Given that our character is not an Ishgardian, we don't have the ability of transforming, even when drinking dragon blood, so I believe it's quite safe (although heretic) to do so.