Super Saiyan Blue is possible because Akira Toryama want's it to be possible. I've come to think that everything is becoming over exaggerated in the DBZ universe. I always thought Goku had a higher purpose in the DBZ, or was some messiah that would stop Buu from destroying the universe. Much like John Connor had a purpose in stopping Skynet....or the Dragonborn in Skyrim's purpose was to defeat Alduin and Miraak and become Hermaoeus Mora's new champion / Immortal demi god champion. Or like Neo who was destined to save everyone in the Matrix. Yet this new series takes away from Goku's destiny as a legendary hero that seemed to have a purpose.....which no longer is that way.