As team members, we can create posts that already can have the status "planned" or even "in progress". We need to provide for team members the ability to set status, estimates, and assign to a team member at the creation.
To avoid duplicates we can show already existed posts when user tries to create a new one.
Now we can create posts only from the board. It's good to have a page with the ability to select a board for post. It also can be embeddable in widget and link to this page or window could be placed in roadmaps.