In Projects creating "Tasks" on template that show on Portal

When using Projects/Workflow all steps are based on "Tasks". Users have requested the when the template is set up, some tasks automatically have certain deliverables that are requested and show up onthe portal. We have the functionality when creating a task from Client Detail-->Activity-->Task-->Show on Portal (making sure we are assigning to contact), but when Tasks are created in Project/Workflow the button "Show on Portal" is there, but the option to assign to an external user is not an option so therefore we cannot get the requested doc to show on portal. Users want that option.