Work in progress notices

Hello,

I'm running a personal wiki with a friend,
and I want to mark some pages as a work in progress,
as well as add them to a category called wip.
preferably with as little repeating as possible,
and also being able to change the notice itself
without changing every page it's on.
I was imagining it would work something like this:

    (:include wip:)

    This is an incomplete page

would get turned into something like this:

    This page is a [[!wip|work in progress]].
    It might be incomplete.

    This is an incomplete page.

I tried to make a page called wip
and include it in a page.
And while it displays nicely it doesn't get added to the wip category,
only the wip page itself is included.

Do you have any ideas how to achieve something like this?

Thanks in advance for your responses.

-- 
Kind Regards,

Aleksandar Sredojevic