Keeping the rust scraped and the scuppers painted will require a full-time crew. Like the workers on the Golden Gate Bridge, they would start on one end and steadily work to the other, and it takes all year. And then they start over. Then there is the problem of the physical artifact itself. A Navy warship is designed to fight in the open seas.
Frills are few.
Open space is limited, and most of those spaces were designed to be locked up. This means visitation is likely to be limited, perhaps to the decks, bridge, hangar and a few other areas. You've got to be fairly nimble to access the heart of the ship, the gun turrets, which means it'll be tough on older visitors and near-impossible for the disabled. But you can't change the accesses, because that means damaging the artifact. This is a problem faced by all keepers of historic ships, and it will be exacerbated by Missouri's great size.