Ok, understand about the request for your client, anyway I find more natural the inverse behaviour…override the global option in every article…
Yes, I know, I think so too, but we have to do what most clients want to have.
About the categories Yes I mean exactly that page
WP allow to write content for categories..there is a way to show in the category page?
Now I know what you mean. Fewest themes support this feature, also this theme doesnt support it.