I hope that you will reconsider your position when the details about modding are announced. Modding in Civ V is more powerful than it ever has been before, and as a modder yourself I think you'll be quite pleasantly surprised by some of the really awesome things Civ V has in store.
I understand that you are referring to the technical situation, and I will assume that you're right.
Yet, as I have pointed out above and will do so again below, there is the legal situation too, and the question in which way DLC will conflict or not with modding has been raised weeks before already.
As you have been silent on this matter, at the moment I have every reason to assume that there will be such legal implications which will prohibit making use of the technical possibilities.
Therefore, I think that your statement is not really accurate.
I can see why you have this opinion - and in Civ IV that might have been the case. But there is no reason that it has to be the case in Civ V. (snip)
2) As for additional civs, it would be entirely feasible to structure the game engine such that it inventoried available civs on launch. If that were the case (and I strongly suspect that this - or something very similar - will be the case), then there is no reason that the presence (or lack thereof) additional civs should prove to be a barrier to mods and modders.
My concern is the following:
Any graphics which come with a certain civilization are under copyright.
So, the (assumed) Babylonian Bowman cannot be taken over in any mod, since that would mean to distribute it to people who may have not bought the deluxe versions.
Yet, even the animation of that Bowman is copyrighted (assuming, there would be a different animation from the 'standard' Archer). So, even re-skinning it and distributing it will not be allowed.
More obvious it becomes when talking about Nebuchadnezar. His graphics (face, body language, background) are copyrighted. Painting a different moustache to him and then distributing will not be allowed.
Same will go then with the (assumed) Babylonian Zikkurat...
All these things are - so I assume from the fact that we have to pay for them and that therefore they are regarded as 'valuable' intellectual property - bound to copyrights and cannot legally be included into a modification and by this being distributed.
Now one could say "So what?".
Yet, the experience from Civ4 tells us that there are many new (fan-created) civilizations which refer to and are based on the standard civilization, graphic-wise.
It is unlikely that this for Civ5 will be allowed - at latest, when DLC comes into play.
And this actually contradicts the technical options, which I don't deny.
It is like buying a Porsche in the US: you
can run it at 280 km/h (you've just bought the small engine

), but you're
not allowed to do so and it might result in major problems for you, if you nevertheless do so.