I think that it's good that this proposal was seriously considered. I don't think it currently beats other megaprojects on impact/solvability/neglectedness, especially since quite a bit of genetic engineering research is already legal in the US (I am once again reminding everyone that human reproductive cloning is legal in many US states, and that it seems unlikely for blue states to enact new laws against reproductive autonomy in a post-Roe era). However, I think that it's good that this proposal was seriously considered, and there should be, on the margin, more proposals like it (in terms of large scale, outside-the-box thinking, potential "weirdness," etc.)
I think I read somewhere that GiveWell doesn't tend to report these figures because the QALY assessment system is so subjective; they instead, for charities focusing on morbidities other than death, report specific results such as "cost per case of blindness averted" or "cost per additional year of school."
I amend my previous comment to replace the phrase "seriously considered" with "considered." Also, there are many state laws against human reproductive cloning, but many states have no such laws:
https://www.thenewatlantis.com/publications/appendix-state-laws-on-human-cloning