My major objection to that is that no such offer to the neighbours exists in the Bible. You're not referring to parts of the story from the much earlier Akkadian or Sumerian versions, are you?
However, if we were to accept this non-Biblical addition, an omniscient God must, by definition, already know they'd turn down any such opportunity to repent.
And to suggest that for the sake of the mere possibillity of saving his neighbours, which, even being generous cannot amount to more than a few hundred people, is to also suggest that the only other people with the potential to be save were conveniently located near to Noah. It seems a bit of a stretch, no?
Doesn't wash, Sandy. Sorry.