Capacity Planning

One of the things I find really difficult to do is estimate what a client's backup storage will be. This is often cause for a lot of confusion and word soup when trying to make a sale on the importance of backup. The biggest thing clients get stuck on is the unknown amount of money it will cost them to implement a backup solution. I sell backup by the TB which is pooled per client. What I'd really like to see is some type of capacity planning built into the backup agent. I want to define the backup plan just like I would on any other system, then run that plan in a special mode (like "Capacity Planning Mode") that will not actually backup data but just totals the amount of storage it would use. Then I'd like to see this data in the dashboard so I can aggregate it across all the endpoints at a customer. This way I can really dial in how much data they can expect to use, and we can extrapolate that out into the future to account for growth. Depending on how detailed these capacity planning reports are, it may even help with optimizing the backup plans themselves (file/folder exclusions, large file backups, file types to include/exclude). But right now I feel like I'm flying blind. I'm working on a capacity planning script that will get me this information per endpoint, but I don't have any way to easily aggregate it.