Why would you want to crop a landscape shot? You have all the time in the world to set up your composition, then you wait for the right light. You should have your framing PERFECT in camera.
My landscape shoots usually take about a week of planning, and about 3 hours of setting up, composing, and sitting and waiting for the light. Get the framing right, and there's absolutely no reason why you should crop a landscape heavily.
I'd worry more about getting a shot worthy of being printed large than pixel count. Landscape photography is challenging but rewarding, and if you want truly gorgeous shots, it's the light, not the pixels, that will make the shot.
Photostiching is nice for panos, but doing it for the sake of getting more in the frame and getting more pixels is manifestly the wrong reason. It's also the wrong way to use a wide angle lens.
Read up about landscape composition, lighting, and actual technique, and don't worry about pixel peeping. Of all the photographic disciplines, you will be massively disappointed if you pixel peep landscapes. Work on your composition and understanding of light.
I love landscape photography more than anything else in the world, and I think you're approaching it in a completely misguided way here.