@nprofile1q... @nprofile1q... @nprofile1q... You are assuming that speakers have some way of communicating with that person. This may be the case for small conferences, for larger ones the person doing the exporting is not always physically present at the event and won't have any contact info passed to speakers.
All of your proposals work for the case where there is an existing understanding of the problem and a process to avoid it. But that is not universal and, when you write the slides, you don't always know what this process looks like so have to assume that it's bad.