Comment We are already on our way to doing it! (Score 1) 409
Step 1: Sequence the genomes of every animal on the planet.
Step 2: Determine computationally how these animals diverged and back calculate a viable ancestor genomes.
Step 3: Build synthetic genomes of those animals that are viable.
Step 4: Transfer those genomes wrapped around histones with the correct modifications back into the an egg.
The technical problems are things like DNA methylation, back calculating genomes, and the fact that we don't know how most non-coding RNA works for organism development.
I'm sure I left out a bunch of stuff but we are currently developing the technology to do all these steps!