I think you will find that disconnecting the servo motor is a simple, costless and GREAT idea---while, obviously, I like everything to work on the car, there is absolutely no need for power door locks in our cars as there are only two doors and you can easily reach the passenger door lock from the driver's seat. I think the problem is, basically, that the system is badly designed. To disconnect the lock motor simply take off the door panel, and stick a long flat screwdriver into the interconnect between the rod from the servo to a plastic bushing that connects servo to locking mechanism and twist the screwdriver. The rod comes out, and the lock/unlock mechanism and push/pull knob inside works easily and smoothly independant of the servo, and the key lock works normally, too. You can reconnect the thing later if you want. I can't be the only person who has hated the power locks and had the same problems you have in cold weather, wet weather etc. The doors would seldom fully lock or unlock, and I always worried about getting locked in the car or breaking the key to unlock the system. Before I disconnected the servo, sometimes I had to push the unlock switch and pull the knob at the same time! When I solved the problem, the fact that the lock worked so easily and normally made the whole car feel better.
--Chris Kennedy