Hi Laura,
I asked around for what our university's policy on retention periods is, and it seems to be a bit different. Instead of an overall maximum retention period, it appears that there is a minimum retention period. So, not in all cases would all the data be deleted once the mandatory retention period has passed. For example, if further research continues on it that was disclosed in some way in the informed consent form, it could be that the data has to be retained. Though I'm still looking into the precise rules that are in place as it seems to be a bit iffy to figure it out exactly.
I can image this would make the idea of a reversed embargo not very practical for our university's set-up.
So, I think we would first have to explore with the different dataverses around the world what the actual retention policy is, before a feature can be developed. I can imagine that the rules outside the EU could differ even more.
Kind regards,
Dieuwertje