Don't know if there are contextual alternates, but Caslon Antique simulates the appearance of worn metal type.

I don't know of one, but it sounds like a great idea. There are certainly wood type inspired faces with alternates for various wooden sorts; I would love to see the same for a lead face.

In the small letterpress house I worked in in my youth we had rarely-used faces—ones that the gaffer considered not worth replacing—in which some characters required two pieces of gummed paper to make them ready. Reproducing this digitally would be nostalgia gone mad I think.