If we go into space, we need enhancements that handle radiation and osteoporosis... or else we're dead. So what seems like an enhancement in one generation becomes life and death in another generation.

What dinosaur traits are missing from an ostrich? The ostrich has a toothless beak, but there are mutations that cause teeth and claws to come back to their mouth and limbs. You need to replace the feathers with scales, but there are no feathers on their legs and feet, so you just need to make its whole body like its legs are.

I would argue that we're not limited by actual DNA. You can re-create the ancient DNA by looking at the genomes of existing animals.

George M. Church Quotes