Well, Let's see. I'm not climbing with it, it is used like a trail of bread crumbs to leave a path. As you stated it's preferred for abrasion resistance, not tensile strength. #36 is used where there may some sharper edges. Braided is preferred over twisted, because it doesn't come undone. I would think anything smaller would be a little difficult to work with, the diameter of #24 is about the right size, to comfortably manipulate with gloves on and one hand. Most guides can accommodate the knots.
As for monitoring the depth, well it's a nice back-up that doesn't depend on batteries.
If I have a zero viz or no mask situation I can feel the line and know what depth I'm at.
Oh, and the OP asked for a simple way to measure distance.
As for monitoring the depth, well it's a nice back-up that doesn't depend on batteries.
Oh, and the OP asked for a simple way to measure distance.