I think you're exactly right to include the automatic tags based on XML features. You will need to add a couple for the new XML features when they go live. Also, you may have missed a couple semi-automatic tags, which are overlapping bonuses and leveled bonuses. This is a little hard because the "override" XML tag can be used for a truly overlapping bonus where 1 territ is part of two bonuses, but it can also be used as a matter of convenience where there are multiple "levels" to a bonus based on how many of a certain kind of territory you have. Further complicating things is that there may be both on a map. Or even territs that fall into both categories.
As for the manual tags, I would like to see a "rail" tag with "rail" defined broadly to include more than just the "rail" series. It should also include maps like Sydney Metro or NYC, I believe. Perhaps some of these fall into the category of a different manual tag like "non-obvious connections": think the cross-map connections on Middle Ages, perhaps every map with bombardments that aren't indicated on the map proper (but in the key) like Waterloo or Stalingrad.
Of course, all this is academic to me until we can actually get some search/organizational functionality to these tags into the site. With 200+ maps, it's time we were able to sort and search by these features, but this is a step in the right direction.
I like that you are thinking in terms of things like "Classic Cities" and I would expand that to other series. Perhaps there could be a "series" tag that would apply to AoR, Draknor (when CMS finishes level 2), the original Rail series, and the U.S. highway/cities/regional maps that have been created. In my opinion the more the better.
Also, it would be nice to tag maps that are produced by some of our more prolific map makers. Not that these maps have necessarily common gameplay, but I think it would be another nice tag to have and also produce some recognition to those dedicated folks. Can you imagine the day when you can start a game on Map: Random: Cairns' maps?
Finally, along with the other topical categorizations (History, Abstract, Geography), you could have subsets of those: History--Warfare or Geography--Asia.
I would say that I presented these things in decreasing order of importance in my opinion. You only have time for so much, but I think categorization is a good thing. Let's say this site gets up to 1000 maps ... it will be nice to have as many ways of organizing these maps as possible. And like I said before, it will be nice when we can finally work these features into the CC search engine so that you can create "limited random" map choices ... for example you might want a Random Complex map (see the other topic on Complexity ratings) or a Random Rail map.