As already pointed out it would not be legal, just to point out: it would also be against forum rules and users doing something like this would not be looked kindly on...
But doing a civ with the same name and with somewhat similar characteristics wouldn't be piracy (list of city names would be slightly different, alternate orthographs work fine too, and units can probably be re-created and look different for a similar gameplay).
Art assets may also exist unlocked in the base game and only be unlocked by the DLC, and be usable by modders no matter what.
Also, this:
All Customized Game Materials created by you are exclusively owned by LICENSOR and/or its licensors (as the case may be) and you hereby transfer, assign and convey to LICENSOR all right, title and interest in and to the Customized Game Materials and LICENSOR and its permitted licensors may use any Customized Game Materials made publicly available to you for any purpose whatsoever, including but not limited to for purposes of advertising and promoting the Software;
is fine but actually not totally legal. In France, there are some rights that cannot be passed. For instance I created a mod. All the rights are automatically passed to licensor, except that the moral rights cannot be transferred, in no legal way ("droit inaliénable et imprescriptible" - article L121-1 of the French
code de la propriété intellectuelle). And these rights mean that I still have something to say about all that licensor does with my work, because laws are superior to this EULA. In particular, there is a divulgation/repentance right which means that (except for software, but it should be ok for art assets - actually for software, one has the right but doesn't have the right to exercise it unless otherwise stated...-) the licensor cannot distribute the mod without the creator's consent and the creator can ask them to stop distributing it whenever they want (but must compensate the licensor for the inconenience caused).
EULA's are fine and all, but the law matters more and publishers can't do all they want.
So, in France, when you say
the legal question of a binding EULA in all countries in which the game is published and to answer all sorts of copyright questions regarding artwork used by modmakers
you're right that they'd be in trouble if they started distributing fan-made stuff and making money out of it (pay per DLC by opposition to inclusion in a free patch for instance), as no matter how they phrase the EULA, they can't prevent the artist from preventing them to distribute the mod. Which I would obviously do if they made money from my work without my consent.
Then again, I doubt they'd do anything to actually harm the modding community, as it would seriously backlash.
