What features are you missing in the invoice and stock management SaaS you use?

So not long ago, I've decided to start building out SaaS' exclusively by user requests, no matter if it's only one user or hundreds. I feel like many of the provided solutions regarding any problem in the SaaS area are not only vaguely similar, but also ignoring those little user requests that can tremendously help the users in their everyday workflow.

So my question for today is, what features would you like to see in an invoicing and stock management SaaS that you think are missing from the vast majority (in the same monthly subscription price range)?

E.g. mass-emailing, reminder scheduling, stock alerts, automated stock renewal etc.