I'd say I'm open minded about egg morphing, and I agree that it would be terrifying...
... But I just can't get over the fact that egg morphing starts to lean more into science fantasy as opposed to science fiction. This IS my opinion, of course, but the idea of a human being transformed to a different organism entirely just doesn't work for me most of the time. There are exceptions though: the flood in halo, the thing, the fly; those worked for me. But other movies that have used similar concepts it just bugged me more than it terrified me. Prometheus and the black goo didn't really do anything for me, nor did the creature transformations in a lot of older movies like leviathan. I really enjoyed district 9, but honestly the human protagonist transforming to a prawn almost killed the movie for me (other factors contributed too; I'm also not a fan of documentary-style movies like the first half of district 9).When that started happening, I almost walked out of the theater, but I'm glad I stuck around to see the rest because it did turn out to be one of my favorite movies in the last 10 years. To me, the most terrifying thing is exactly what alien did; turn a human into a living incubator!