Allow for unlimited Collaborator users, whom can not edit items, but they can view and comment.
It would be great to enable us to have Users that are just clients who can see their own resources and comment, but not edit those resources. Wrike calls these Collaborators and they don't use up your allotted seats.
This would allow a client to keep track of projects so that the "Are you done yet?!" "What are you doing with my website?!" calls and emails would stop.
If they can comment, it provides a less confrontational [than a phone call or email] space to help effect development or compliment developers.
I realise this may go against your business model a little bit, but i have gained 30 clients in the last year and i'm growing fast. I can't afford for 6+ people at each client company to be able to log in as a user, when each user might only log in a few times a month to check on status.