Casting is unfortunately an often useless and ill designed feature in Pike; that might account for some of the dispassion. You can only cast to primitive types, and value casts don't necessarily work, even if you know a value to be a string and want to cast it to an int, when declared a string|int. It's a system difficult to grow incrementally better too, unfortunately.
I think you will have to exemplify a bit. Generally I think casts should be used sparingly in any language with some sort of typeing, and I don't think adding more complex casts would really improve things in Pike. Some examples that illustrate why it would be nice could perhaps sway me though.