Agreed with serpent, pisa is still allied with the aztecs, but its AI might not drag them into offensive wars with aquitaine that the imperium can intervene in and the aztecs would not. The aztecs, and maybe other foes of the imperium should get a bonus to unjustified demands and AE impact so the AI is more greedy; the horde took a pretty good chunk of land, but it was paid back to the imperium with interest. Now, they could always bounce back, espeically since a lot of aztec land in europe is of its own culture (so does that mean we wouldn't be able convert it unless we totally destroyed them?), so the cores won't be going anywhere anytime soon, but I doubt the whole of egypt could be lost in one disastrous war again like it was in CK2.