I have a handful of immortals that have spent the last 6000 years stuck on planet Earth. They really, want to get out of here. They missed their chance back in Egypt before The Fall of the Pharaohs**. This time around they aren't going to miss the next opportunity off this rock. They are planning ahead.
In the next 100-200 years, we will develop generation ships to take us to the stars. Explore the cosmos, colonize space and new planets and all that. Everyone is very excited, including the immortals. Currently they are hiding in plain sight, moving every few years/decades etc. Unfortunately the concealment methods they have been using will be reduced on the Generation Ships.
At first they wondered how they would hide on a generation ship, then they realized they first needed to figure out what type of generation ship to travel on. They know that they won't be able to hide their immortality on the initial smaller generation ships. They have experimented, and all signs point to cryogenics not working for them. As long as the Second Fall doesn't happen anytime soon, they have to wait for one of the larger capacity generation ships.
They aren't worried about the design of the engines or fuel. Well they are, but they are more worried about the social structure and spatial planning of the ships. They have been studying up on psychology, urban spaces and social engineering etc. They can become leading experts in the fields necessary to influence how the Ships social spaces and human movements around the ship etc are planned, well before we ever leave the planet.
What sort of generation-ship design would allow a handful of immortals to remain hidden? ***
Answers should take into account the ability to hide a handful of un-aging individuals in a relatively small population (compared to overpopulated Earth), as well as in a confined space. The immortals wish to remain anonymous, they have the same mental health requirements as a typical human (they don't want to go hide in a corner very often). A good answer is one that somehow incorporates multiple concealment redundancies into the ship-design, just in-case someone catches onto them. Users can determine how big the ship will need to be. Answers should try not focus on the method of Engine design/feasibility but rather on the social aspect.
The immortals are willing to be live separately so as to avoid suspicion, and have committed to no reproduction while in-transit. Transit will take 5-10 generations.
**The Fall is when a highly sophisticated civilization falls so far backwards in progress, that later populations believe they are the first to become so advanced.
*** This is not a homework question.