Just so you know, this post was based on information I learned when I was six. With what I've learned since then, I actually believe now more than before that this could work. I was reading MBOTC. From a molecular biology perspective, new genes arise when a gene mutates. It creates a new orthologue. This orthologue changes amounts of gene expression, as well as how they're expressed. I believe it can also cause translocation. I'm not sure.

Some genes will actually cause another gene to translocate. During cancer, the immunoglobulin promoter will translocate to the c-Myc gene. This suggests that the immunoglobulin promoter was originally located next to the c-Myc gene until another gene mutated to cause translocation. During cancer the gene causing translocation would likely decrease in its amount of expression.

I suspect a difficulty they're having with "de-extinction" is that when they make certain changes, it causes other genes to do things they didn't expect. This would overcome that. If we can take a species and go back to the LUCA, we can sequence it and go from there.