As a Freelancer turned agency owner (who loves working with prismic) one of the pain points I have is handing over to clients
I suggest a way of creating a 'team' that's not tied to any repository, but can easily be added to multiple repositories to allow for developer edits.
This agency team could then pay for seats on their own plan. Pricing is obviously up to you, but i'd imagine a seat based pricing structure similar to what already exists for editors - but better suited to agency workflows.
This would solve a lot of issues I come across as an agency owner, but many of these issues also persist for solo freelancers (especially handover problems). I'll try to list them all below
Handing over to a client would no longer require contacting prismic to remove card details or downgrading to the 'starter' plan. The agency would pay for their own members as part of the agency plan, so the client wouldn't need to pay anything until they add their own team, and there's no awkward steps to give the client the repository that they own
Managing team members is easier as it all happens in one place. Agency members have repositories assigned to them (or agencies have repositories assigned to them), rather than having to assign new members in each repository individually.
Agencies no longer have to keep track of which repositories they pay for, and which are paid for by clients. Agency payment is handled all in one place, and the client is always responsible for their editors.
Clients can't accidentally remove team members from the agency that they don't recognise
Client seats aren't wasted on developers when (especially for smaller businesses) seats are precious. With 3 developers, client has 4 seats remaining (3 for editors, one for themselves) before pricing grows substantially.
I'm sure there are more reasons to take this approach and I've only thought of this from a development agency perspective but I'm sure there are content creation agencies out there and various freelancer types who run into similar problems