A new civ runs tendrils throughout the game mechanics; new UUs, UBs, artstyles, leader, etc, etc. Modularlizing this, while possible (and is done by many civ4 mods), will create compatibility and development nightmares, no matter how it's implemented. Perhaps Shafer was misinformed when he made his statements about exposing the dll, but I don't see how one is going to be able to package majore overhaul mods like RevDCM for the new modding download hub, that will be able to take into account the shattered codebase that will result from a DLC aproach to adding content. Just look at Civ4 mods as an example, you can't just pick and choose modules; some mods claim that they can be added this way, but in practice it simply does not work.