Cutting DNA in vivo can be a messy proposition compared to regulating it sometimes even if the artificial not-tuned-by-evolution regulation is at times low-precision.

Agreed. large scale editing of the genome is unacceptably risky. I imagine that biological transhumanism, if we bother before uploading, would be more likely to something like a HAC (human artificial chromosome). There are plenty of steps in the network above to interfere with, we don't need to incur the risk of malignancy or cell damage that would result from large scale editing of the genome. Even a method that was 99% accurate would be unacceptable.