Provide the ability for an alternative means of adding external (non-SF) project participants, (such as a customer contact) to tasks. Currently, this is only possible if the user is the task owner or by adding a custom field(s) to the the task object.
It’s not reasonable to expect a bunch of queues to be set up for random groups of project participants. And, External Sharing allows communication of the project data to outside entities but does not confer any ownership or accountability that can be attributed to a person who is responsible for the task(s).
Not every Task Ray participant in a project is going to be a SF user in our instance. There need to be some form of object or set of fields that permit Contacts or even just a list of project participants to be included in tasks even when those participants are not users. Even if they were users, only one user can be assigned to the task owner, when it’s clear in most PM products that any number of people can be assigned to a task (or even groups).
While it may be in everyone's interest to help Salesforce increase the user community, that is not realistic when simply trying to convey accountability for tasks and communicate that to customer management.