Rushmore IMO is one of the best map specific or unique additions to a zombies map.
I hate Alpha Omega, its one of my least favorite maps of all time but Rushmore is one of the few things that i consider that this map has that are very good.
He is literally the heart of the map, he has a very charismatic and charmful personality, I think he is better than S.O.P.H.I.A in Gorod Krovi.
You can also interact with him and know more about the map, he can tell jokes, etc
He has a lot of codes that you can put into him that can give you very useful stuff like a undead man walking or a bonfire sale
Please treyarch, if you are going to make a Alpha Omega, please keep Rushmore on the map