correct, as Akito told Ikki...he needed to find the parts and create a regalia totally for himself. aka the Storm regalia.
As for the Sky regalia...i think its probably a regalia that is just as powerful as the other regalias, but can equip the known 8 regalias onto it to make it even stronger. Because when Sora was talking to Spitfire before killing him, he said he would just wait to take the Flame regalia from Kazu if he were to pass it to him. meaning he might want the regalia to combine together.