I tried to suggest this idea to Squad and never heard anything back. However it is a simple idea, and easy to explain.
Mission Idea: Large cylindrical object enters the Kerbal system, you are told about it in a prompt, its size (20 kilometres (12 mi) in diameter and 54 kilometres (34 mi) long). Your mission is to rendezvous with this object and collect science with the stock science instruments in various places, including inside it (once you figure out how to get inside). That's it, that's the mission. Science text would be from the book more or less so that the data will slowly allow you to figure out Rama and its purpose/workings. Views from inside Rama could potentially be stunning. Craft could either be given to the player or alternatively they can construct it themselves given a few (just enough) constraints.
Potential issues:
In the book Rama has a very high velocity, might be reasonable to reduce it for easier orbit matching.
How do you make a 30 mile long cylinder in KSP with water, or at least blue deck plating or perhaps a large ditch?
Clouds in a player made vehicle???
