I think many of us love to add external figure (clients, collab...) to a list or project not as part of the team but only for minimal interaction (but not only viewer). In many cases the free guest number is lower than the real necessities and pay a full seat for a simply interaction on temporary or specific tasks is absolutely not sustainible.

So...why don't you think to a plan for adding guest seats to a space?

I.e.: 10$/month for 25 guests