Do you have experience with features for Agencies in a SaaS product?

Hi,
Form-Data is a backend for webforms.
It works well and has steadily growing base of customers.
Most customers are on the freemium tier, which is no surprise.
The ones that I'm able to convert are either small businesses that have higher submission rate, or agencies with multiple customers.

I feel that the next growth opportunity is with the later group.

Do you have any experience with developing specific features targeted towards agencies? Of course I'm also going to ask my customers, but I want to be prepared with some ideas.

Some ideas that I've collected during the years:

• Sub accounts so each end-customer can login to their own sub-account and manage only their own data
• More granular roles so the agency can allow their customer to see the form-submissions, but not edit the forms configuration
• Billing reports per end-customer
• Charge the customer + rev-share: each end-customer pays for their own sub-account, possibly more than what I charge the agency. The agency takes the extra revenue
• White labeling of sub-accounts
• hand-over of a sub-account to the end-customer - build and then give the keys to the customer

If you have some experience with such customers I'll be happy to hear what worked well or what didn't.

Thanks!