I'm a sole proprietor and I work in video, so the files can be very large - I can routinely be working with hundreds of GB on any given day. I currently have the Professional plan that allows 3TB of storage and I'm almost always maxing it out. My plan only allows an additional 1TB upgrade which I would use up very quickly. I want to suggest that you offer larger storage upgrade options for a plan like mine, say 5TB or 10TB. I would gladly pay an additional fee yearly to get more storage space.
I know you have the advanced plan, but I don't have a team, so I don't want to pay for purchasing additional licenses just to get additional storage space.