Hello Ben, I've just recieved a reply to the application for my character, and agree with your responce. however I believe there was misconceptions as to the Kekkei Genkai and genetic material used.
Eboneraz Azimuth was a Kaguya by birth, obtained by Danzo Shimura using his Root Nin. Who planned to have him as secret weapon of Konohakure without anyone realizing he existed, Ebon had no choice as to the experiments placed upon him and was subject to the Root Program. The Uzumaki Dna was stolen from Kushina Uzumaki shortly after her death and injected to increase his Chakra reserves at the cost of his control. however before he could be completely controlled he fled, stealing the Kage Bushin and Edo Tensei Techniques to weaken Konoha and by extend Danzo. By birth he was the son of a unnamed Kaguya and a Bakuton user.
I wont make another application for Uzumaki Dna. however I thought you would like a more detailed explaination.
Well, is reason of survival is basic and common. He hid away. It is boring and used often. Itachi too, would be one to search every nook and cranny to ensure Danzou would be happy enough to not kill Sasuke. That is one of the main reasons I'd think of. The reason too is kind of bland for why you want him.
Try to make it unique. Make it good, and make it make sense. It is hard for Uchiha to have survived in Konoha as Itachi is a wrecking machine. Think outside of that. Think further on why you want your character as an Uchiha and how much if is truly significant.