I would keep investigating the Mexican connection. It is true that we don’t know of anyone on here that has bought a turn-key car from them, but a lot of that is because we only recommend buying from three or four builders and don’t have any experience with Classic Cars Mexico.
Yes, importing may have issues, so check with your state RMV before you commit to a build to make sure it’s register-able in your state.
Of course, the best thing would be to visit the builder during the build and just before delivery to make sure there aren’t any “got’chas”, but that is up to you and what you feel comfortable with.
Keep us posted on what you find. We might all find a new builder!