We have been discussing roundtripped document binding before, and I did some work on it. If you think it's worth, I'd happily suggest another release candidate.
In the moment, a repeat SDT is multiplied into several SDTs stripped off, all these SDTs not tagged any more. I changed this into the first SDT unchanged, the following denoted by an empty repeat-tag "od:repeat=". On a second run on this document, the first SDT is then re-used ...