OK, I'm just thinking out loud here,
but if your wallet can take it,
buying a "Log Haul" kit from SierraWest models,
and adapting the "chain cleats" so that they grab the uphill axle of the car, <may> just be the ticket
Have the chain set up like a human escellator,
and "dropping thru a hole" at the top of the haulage,
returning downhill upside down under the landform,
to make a "continuous chain" system.
For power, can I suggest the "Gearhead + Motor" combination masquerading as the MicroMark "SwitchTender" turnout motor.
http://www.micromark.com/SWITCH-TENDER- ... ,8394.html
It is working for me as the powerplant for a worm-drive traverser mech, and nicely "stalls" at each end of it's travel,
(or if anything "catches" in the haulage system that would otherwise kill the motor or damage the mech
without overloading/burning out...
might be worth a look...