Now that I have had two nights to think about it, I think I can tell what is wrong with the Civ5 DLC scheme. The issue is that, on the one hand, conceptually, DLC is neither inherently good nor bad; on the other hand, what you sell as DLC can inherently turn people off or on. My feeling is that actual historical civs are not appropriate to sell as DLC. If you make a Babylon civ, you should include it in the regular edition, or in regular editions of expansion packs. But if you make a race of dwarves and elves, with all the required art for such fictional races, then I think you can sell that as DLC.
On a related note, civ-specific graphics art might be nice DLC to sell. Having played mods such as Fall from Heaven, Earth 35, and The Ancient Mediterranean, I am completely aware that there is no good reason other than economical reasons not to create civ-specific units. I have never been confused by the different looks of military units on any mod and anyone who claims otherwise are clueless. Civ-specific art only adds to the aesthetic value of the game--they do not distract from gameplay at all. Perhaps, Firaxis cannot make as much profit making interesting looking games. Perhaps, they may correct this by selling additional art as DLC. Expectations are the cause of disappointment here. We expect not to pay extra for Babylon. But a race of dragons or vampires or extra art and maps--well, that's different.
Map packs should be considered fair game by consumers for Firaxis to sell as DLC. But map packs probably would not compel most people to purchase them without good cause. Those maps had better be good. Firaxis should allow for DLC purchasers to leave feedback and grades so that other people who have not purchased them can evaluate whether they are worth buying.
The only DLC civfans may willingly and gladly spend $10 or more on are complete mod conversions or scenarios. But only if these mods or scenarios are given the polished finish of a professional work and are not hack jobs. And it would help if at least two or three employees were kept on to tweak and improve these. This would make the least economical sense for Firaxis, but this is the ideal DLC for consumers, I think. Subscription would not work, I don't think, for civfans. I would not buy mods based on subscription if Firaxis adopted a subscription-based model since I expect that free user-generated content may be competitive with or better official mod conversions. But perhaps you can make users re-purchase with discount the full mod conversion after any significant improvements are made, such as mod updates after expansion packs. I think I could buy the same mod again if a "service pack" is released. Or perhaps I could buy the service pack alone.
But if the only things that make economical sense for DLC is selling additional civs and non-compelling map packs, then I think Firaxis will have to accept some amount of backlash and go ahead and sell it as DLC.
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"awesome" indeed. 
