Is it an option for this team to have a private group set up so they can co-author the excel before it is moved into a public space? that seems to be a workaround for now that we have been using in our community.
Even if they were in a private group, they would still have the issue. Each team member needs to plug their numbers into a slide... and no-one knows who has downloaded and is editing. We are using Mark as Reserved as an interim. Also I have restricted authors on the PPT and asked people to plug numbers into a Jive Doc. But it is duplication and not totally efficient.