Creating Post “Sets”

Hi, all. Bit of a complicated one, this.

I run a blog in which posts follow a weekly theme. That is, an image gets posted on Sunday, and every day until the following Saturday, writers respond to that image.

One of the features that I’d like to create is the ability, when in an older post, to navigate to other posts and the image from that week. At the moment, that sort of navigation is replicated by a “six most recent posts” widget and a “one most recent image category post” widget, but naturally that doesn’t help someone reading a piece from months ago, and wanting to easily navigate to the other pieces from that week.

I have found a potential workaround in using the lovely Related Posts plug-in and WP’s native tags – I simply go through and give each post in a week a tag that indicates the first date in that week.

The only problem with this is, it excludes the use of further tags, if I want it to work properly. And that seems a shame, if I end up wanting to use the tags for more directed navigation later.

Can anyone think of any solutions to this? The best way of thinking about it is a function like Flickr’s “sets”, wherein each week of posts is also linked to a “set”. But I have no idea if there is a plug-in or anything to do this already…

I look forward to your suggestions!