The system is designed to allow a one-way acceptance to avoid inundating the manager (or supervisor if permissions are allowed) with too many notifications, emails, and general back and forth. During our testing we found that this caused inefficiency outside of the design of Zip Schedules, which is purposefully simple.
As you mention a common practice is to offer the shift to all available employees in one go (the system will prioritize employees who are available to the top for you), and actually the system will assign the shift to the first employee who accepts it.
The idea of unassigned shift visibility for all employees is a good one though, and we will take the problem back to our design team. There may be an opportunity to include this in the Team Center for Crew-level users.
Hope this helps,
Steve Gordon - Altametrics
Customer Success Manager