The Updates feature of developer sandboxes is very useful to keep our sandboxes up to date with changes flowing through our pipeline. We are running into an issue though when using it within a Long-Term Project. We've faced scenarios where we need to either refresh or create a new sandbox and integrate it as a dev sandbox feeding into the Long-Term Project's final static org. We have no easy way to catch that dev sandbox up to the current state of the static org because the metadata promoted there hasn't been released to Production yet.
It would be very helpful if you could "seed" a dev sandbox with Updates from its downstream org by selecting a recent promotion. I imagine that change, along with all changes that occurred after it, would appear as Updates in the selected dev sandbox. This would save us a ton of time since we don't need to manually compare and deploy a bunch of changes to catch the sandbox back up to the current Long-Term Project state.