All lane departure does is jiggle the steering wheel.
It does now gently pull you back into the lane (this may be a setting).
But back to the OP's original question, which is a bit confusing.
You (OP) say that lane assist is "needed", yet "autopilot is impractical". I am very confused by this, since it seems like the function you are asking for (keeping the car in the lane) is precisely what autopilot does (well, that, and the fact that it's "needed" is a bit questionable as well--obviously it is possible to actually drive the car manually on those roads).
It sounds like the function you are asking for is what Tesla calls "autosteer". "Autopilot" is "Autosteer" + "TACC", so yes, technically Autopilot is more than just simple lane keeping. So I am inferring that the reason you feel that Autopilot is inappropriate on your hilly, curvy roads is that you don't feel comfortable with the speed that it's taking those curves at (although it will slow down if it feels like it needs to, so maybe your tolerance to its speed is a bit low).
If that's the case, then here's the solution. Go ahead and engage Autopilot, but set the speed to a really low value. This will require you to use the accelerator pedal to maintain the speed you are comfortable with, but that's what you wanted anyway. Voila: you have autosteer without it taking turns at too high a speed.