Well, I'm dubious about the new startdate (it makes me worry 1066 will not be balanced to avoid the ahistorical destruction of European pagans since you can "solve" that problem by starting earlier), and the focus on Vikings is meh, but... the rest of it is so lovely I'll buy it gleefully anyway with the highest hopes! There may have been schoolgirl-like tittering at the ridiculous but awesome inclusion of specific mention of Zoroastrians and bringing them back to power, even. Even with the focus on the Vikings (and I do understand they're marketable and Scandinavian and thus the focus on them), the fact most/all the pagan factions are getting unique mechanics is wonderful and I will be very happy to give you my money for it.
There are two big things I hope for.
1) As above, please please please include some changes that make the Romuva and Suomensko factions not instantly get conquered in 1066. Lithuania should have a chance to survive and thrive as it historically did, so there must be some way for small pagan countries to stave off conquest by the Big Grey Horde and even successfully expand.
2) It would be great if you could please consider some method to actually play the Aztecs in their invasion. Perhaps something like the republic "family palace" can be used to make the Aztec Emperor not truly landless, and then one could direct the initial invasion fleets? I presume they'll be made playable and localised in this DLC, but it'd be much cooler to play them yourself (even if only at a 1250 startdate or special bookmark) rather than having to let the AI Aztecs arrive and grab somewhere before you could switch to them (as their arrival can be many years after 1250, and their success varies wildly, this may require multiple restarts to get something enjoyable to play). Something like that could be used for Mongols too, of course.