Oh, I would definitely do that, there would be a WIP thread. My only concern is that lots of times when I visit a site like cgtalk, etc., I go to the showcase or finished works forum looking for new things to see. I won't necessarily go through multi-page WIPs to see if any of them are finished. It just seems to me that doing it this way, only folks that have been following the WIP will ever see your finished project. If there is a forum for finished works, you can go there and quickly scan the thread titles to find things you want to see.
If I upload an image to A:M Stills and post to my WIP that it's done, there's really no announcement to the world to say "Hey, come see what I did!"
Just my ¢2,
Richard