Another thing to factor in all of this is micro-fauna; parasite resistance and symbiotic parasite loads that we can not replace. If we bring back any of these,

Another thing to factor in all of this is micro-fauna; parasite resistance and symbiotic parasite loads that we can not replace. If we bring back any of these, we need to insure a way to offer them resistance to new disease, and offer them symbiotic micro-fauna that their bodies can handle, so they do not just die of internal disease and get eaten alive by what would normally be a good bacteria to say a modern mammal.