Number one, why would kuja be riding on the back of his dragon, when if hes off, in trace, he can still fly. This way 2 people could be attacking raziel. Sure raziel can tk kuja, but that will drain raziel's mana, or the equivalent wouldnt it? And as stated before, it will do reduced damage to kuja anyway.

YOu say he can posess....in what game have you EVER had the ability to posess a boss?? This case shoudl be no different. Raziel can try all he wants, but he shoulnt be able to do it. All hell be doing is draining his mana reserves.

You say tha tthe soul reaver can bring down the cathedral? How and why the hell would raziel do that. He brings it down, he has a huge chance of boulders of SOLID ROCK falling on him. If he does manage to bring it down with a SWORD, mind you its not a grenade, hell be doing kuja a favor. He wont be able to materialzie into the material world without solidifying in solid rock.