Maybe: just a free suggestion or two.
As you already know, if you want to leave the rolling stock on the
rails, your problem will be raising and lowering it level and gently,
so I would recommend a hand winch (marine supplies?, preferably one
with a break, if such exists, perhaps the winch for a small boat
trailer). This will also let you handle more weight than you could
carefully by hand. (And Murphy's law: one day a child, the dog,
Better Half, the telephone is going to surprise you in the middle of
the action. :)
Obviously, lines from the corners of the board (that is going to have
to be stiff enough or reinforced to avoid sag). I would use plastic
covered steel cable, 1/8th inch should be strong enough, probably
less; ask when you buy it and know what the layout weighs. Anchoring
the pulleys could be a problem some places, but I expect this isn't a
room with a plaster board ceiling.
Now we come to the tricky bit: all the cables have to move at the
same speed and have to go to a pulley or two directly over the winch,
yeah, two pulleys, each large enough to take two cables, and since
they are coming from different angles, a lead to guide them into the
pulleys is needed, otherwise a cable will jump off the roller, clamp,
...! A sturdy eye-ring should do the job.
Now the difficulty is attaching the cables to the drum of the winch so
that they all have equal tension. I don't know what the winch will
have to hold the single cable it is built for. I would clamp all the
cables together with little screw clamps made for this purpose, but I
don't know if they exist for such small cable, otherwise I would bind
them together with fine wire.
About the equal tension, I just realized that you can't pull the board
right up to the ceiling, so the tension could be adjusted by
turnbuckles on each cable, which is ideal, since maybe they do
stretch. And since you probably want to unhook them when the layout
has been lowered, they will add weight so that one doesn't
accidentally fly up to the ceiling.
What did I forget, or what questions do you have? As you can tell,
this is just off the top of my head, and I haven't gone back to check
for mistakes or omissions.