I want my scheduling interface to tell people which times are most convenient for me, while still allowing them to pick other times.
Open slots should show up as preferred/recommended/suggested times with yellow background color based on pre-specified time windows, or based on whether they're taking place right before/after existing meetings (to batch meetings together).
Usually, people hire executive assistants for this, but it can be done by SavvyCal instead. I think this would be a killer feature that none of the other scheduling tools have!