Well, it's kind of wondering me lately that why in LET, they didn't also use EVA's eggs to create the clones but of some Japanese woman instead? Is there anything wrong with EVA's DNA that couldn't be used for the project, like congenital disease?
No explanation is really given. From a writing perspective, it's because Snake needed to have some Japanese DNA in him. I'm not sure why this reason was chosen over having Big Boss (or EVA) be of Japanese descent though.
Storywise, it's possible the surrogate mother may only have been chosen after viable embryos had been produced. Or, perhaps EVA's eggs just weren't suitable for the procedure, as they specifically refer to the egg donor as being "a healthy Japanese woman."
18.104.22.168 wrote: I guess because EVA is the character that's been written after the "a healthy Japanese" infomation so they can't let her be the eggs donor, huh?
Not quite. Both characters' connection to LET were revealed in the same game (MGS4), so the writers could have made EVA the donor, but decided not to. But yeah, EVA's character was written way after Solid Snake's Japanese ancestry was known.