I'm totally with you on this, it's important to keep re-aligning with positive outcomes and reminding others that negativity and "being a realist" are not the same things.
I'm not the first to say that AGI would probably map, explore, and populate the galaxy with life long before we would ever be able to make it past proxima centauri on our own, but it has occurred to me that VR would be a wonderful way for the AGI to show humanity what other worlds are like if it was inclined to do so. I know that I would personally feel honored to have a front row seat to something like that.

I think the consideration here is stem cells. The aging process involves the deterioration of DNA because the body does not produce more stem cells - as it runs out, it loses the ability to maintain the integrity of its DNA. It's tempting to think that by regularly refreshing the integrity of the DNA by uploading a configuration from when you were 20 you would stave off that deterioration, but an aging body isn't capable of following the instructions that that young DNA would give it because it lacks the regenerative cells to do so. On top of that, our genes expressing differently over the course of our lives (before senescence) is not a bad thing and you might very well cause unintended damage by trying to force, say, a 35-year-old's body to abide by the gene expressions of his 20-year-old body. What if you tell his bones to shrink (which I don't think bones are capable of doing), or what if his immune system decides that all the hormonal stuff caused by "second puberty" was a bad move? What if the sudden and regular changes in gene expression reads to his body as "we are in an environment that is so stressful that it altered our gene expressions holy FUCK PANIC!!!" and now he's allergic to everything and permanently drowning in cortisol?

I could see your idea working with the addition of new stem cells and probably a lot of case studies, but you can't treat genes like they're a coding language and the body like it's a computer. It's a silly goopy mess of hormones and microbiomes and it's a miracle the darn things work in the first place so we can't expect bodies to behave themselves however would be most convenient for CRISPR.

Final thought: if gene expressions were the end all be all of what shapes a body, you could slap some horse DNA into CRISPR and horse-ify yourself. What would actually come out of that process would be... Well, not a horse.

I think it's kind of like "could probably be achieved now with some chutzpah, could DEFINITELY be achieved after AGI". The tools do exist, it's just a matter of whether or not someone could get that startup all the way off the ground before an AGI rolls around.

While the actual physical process of altering genes might be relatively simple thanks to CRISPR, the technical knowledge of how to do so correctly and beneficially remains too complicated for in-house gene editing. It's so, so far beyond just being math or chemistry - we have human DNA mapped but we don't have gene expression "groups" fully mapped and we certainly can't say for sure what EXACTLY will happen any time a given gene is toggled. Some gene expressions could take decades (or generations!) to express, so the consequences of a gene edit gone awry might not be felt for a very long time.

That being said, specialized AI could probably catalogue and map all gene expressions like how modern narrow AIs are capable of generating and understanding proteins that haven't even been discovered. Such an AI in tandem with whatever device could be scaled on the market such that everyone could have one in their home would probably be all it takes. I don't know enough about this to know what that device would be like, so maybe there's some hurdles on that front... But, you know. Technology. It do be advancing, hurdles are always temporary.

There's your big tech startup idea! Just gotta train the AI and voila.