Instead of a hoist how about a set of rails. I vacationed at Tomales Bay and the house next door had a 30 footer that was hauled up on a bunk that rolled up two steel I beams. For a kayak, you might tie off on the wall, up a ladder and then winch up the TI/AI up PVC tubes, kind of like building a trailer. In Jack London Square at the kayak rental place, they have plastic floating docks, that the kayaks can beach and are partially buoyant. Home Depot has a kit with wheels, you could use PVC instead of the wheels.
http://www.homedepot.com/p/Unbranded-1200-lb-Capacity-Kit-for-Boat-Ramp-SD-1200/203916673 I realize the grade is not as severe as you would need it to be. The house in Tomales as at least 45 degrees. It can be done.
There is a post on this forum of someone that built a ramp, again the slope is not as severe as you would need, but you get the idea.
http://www.hobiecat.com/forums/viewtopic.php?f=14&t=10603&p=55939#p55939