i disagree,I don't think you know or understand much about the Mesopotamian pantheons. Do you know about how the Egyptian pantheon developed from a bunch of different local animal gods? Was the religion "destroyed" when later Pharaonic powers assimilated them into a pantheon?
Ptolmy and his successors NEEDED the support of the priesthood so they only made minor administrative adjustments in relations to funding, and not religious dogma or practice, in effect the only major changes were the introduction of Serapis to appease the Alexandrine greeks. the same can't be said of Sumerian religion as their deities were related to cities and kingdoms, so when a kingdom is destroyed so is its religion, some deities are assimilated but this DOES NOT show, justify or prove continuity as the deities were added to by late kingdoms.
I am sorry to disappoint you, but i do possess some knowledge of the evolution of Egyptian religion. firstly you misunderstand the Egyptian situation, Egypt was invaded by many nations and barbarians alike. however, none of the invaders left any permanent mark or caused any real change to the corpus of beliefs and religious bearings that the Egyptians held (apart from the muslims). also your scenario regarding the Pharaonic assimilation of local animal gods, is not in anyway analogous to the Sumerian situation, for the following reasons:
1) Egypt with its religion and language, remained united, this meant that no assimilation, change or alteration can occur as the pharaohs did not change the pantheon, they merely expounded and elaborated on the beliefs.
2) Sumer was a kingdom among MANY kingdoms in Mesopotamia, and whilst it was influential on other cultures in the region, it in no way was the benchmark or common culture of the region. Sumer's glory declined greatly in the second millenium BC and this led to the gradual disintegration, if not disassociation of their religion.
3) the religion of Sumer evolved to become anthropocentric. Although this within itself does not constitute a discontinuation within the religion, it had a great influence on causing the fall of Sumerian religion whenever the Sumerian kingdom dissolved. this is because the Gods were related to the cities and towns (ironically the best example comes from the Egyptian Pantheon in the form of the god Ptah being the major deity in Memphis) this association ensured that when the city was conquered by an invading culture, the god of the city would be forsaken as they were defeated.
4) there is not much evidence to suggest that the religions of mesopotamia were the same. However i would agree that they had a similar basis, this does not mean continuation as Christianity IS a separate religion from Judaism, and Islam is not in continuity with either Judaism or Christianity. this example highlights that whilst sharing a similar foundation, religions that are similar are not in continuity with each other----> directly analogous to the Mesopotamian situation.
Hope you have a nice day