I think this is a good question, Faithlilly.
Hypothetical questions are valuable.
I would like to see the Smith family re-interviewed. I think that there could be a lot more information there, if the Smiths were required to go over things again very thoroughly and in response, perhaps, to being presented with new questions based on information SY may now have.
The question of why bundleman was walking around with Madeleine at that time is a central part of our problem in determining the story behind Madeleine's disappearance. Even the tiniest new detail could help us build up a clearer picture of exactly what was going on at that stage of the evening, which might help narrow down the number of theories there are as to what kind of abduction it was. (Perhaps SY have got beyond determining this, though so far there doesn't seem to be much to suggest it. The Smiths could be helpful either way.)
Mr Smith seems to be quite a low-key person who does not want to court publicity in any way, and so the information he has given has been at a minimum, but there is a chance that he would have more to say if re-interviewed today.