The point of God Serena not having the big eyebrows like Yuri can simply be because it's a different angle.
Erza is allowed to go on the mission. She's proven that she can coordinate small party missions like with the Lullaby arc. She's also one of the few people that could protect the group if need be.
The complaints about Natsu getting stronger and then beating the enemies: this has been consistent since the beginning. Also, Hiro told us that Natsu's flames get stronger with his emotions.
I feel like B Team is gonna end up going to Arbaless looking for Laxus, and will get caught up in the fights with the 12 shields of spriggan that will inevitably happen.
Natsu will probably fight God Serena and win after a while, probably with help from gajeel, wendy, and erza.
(Assuming Yuri is God Serena) Yuri probably doesn't know exactly where Lumen Histiore is. He may know it's with Fairy Tail, but its exact location may be unknown. Maybe he went dark after fairy tail disbanded to try and revive Mavis.