Multisite category landing page subsites

I hope I can explain this enough to make some sense. I have a multisite set up and am using Sitewide Tags to pull links from new posts on the subsites to the main “portal” site. Everything is working like a charm. I have it set up so when somebody clicks on “read more” on an excerpt shown on the main page they are sent to the actual subsite to read the original post.

Now what I would like to do is create subsites for the different categories that function the same way as the main home page but use a different theme. For example, if somebody on subsite “A” makes a post and puts it in Category “Stuff”, I want a link to be sent automatically to the main page “recent network articles” along with post links for that category and all other categories,(which is what I have working so far).

The next step I would like to do is create a subsite for the “Stuff” category that also shows the link to the original article along with all the other “Stuff” category posts. I would like it to be a subsite so I can use different themes for each category along with different category specific widgets and such. I wouldn’t mind if I were to use categories, tags, or both to make this happen if that helps.

Thanks so much for any ideas!