Tags, categories or attributes for thematic item?

for a new website I need to use categories as geographic categories and I need to have something to indicate the pre-established thematic, just think about a news site with geographics categories full of posts with "economy" "chronicle" topic etc.

  • Categories: if I’ll use them I’ll have to find a way to separate the geographic cat from the thematic one in order to echo the second as topic in post listing.

  • Tag: the editor will no longer be able to use tags for other things, maybe seo etc

  • Attributes: it seems the best way, but how I can give to editor a default list instead of use them as text field in each post?

Any idea or suggestion?