How can we make the assignment field on future tasks entry capable?
If the assignment field on future tasks in the workflow are made display only, then this indicates that the current user does not have permission to reassign tasks. That permission is granted here: Phire Architect > Security Administration > Reassign Task Security. The permission is granted to either a role or an individual user, similar to the other permission sin Phire. And it can be granted to all task types, or specific task types depending on the requirements being met.