I’ve read over this a few times, seems very thorough. A couple thoughts.
If the user has access to the “Your Directory Entry” profile admin page and they add their details there, there is no need to logout/login for the link to be added between the WordPress user and the Connections entry. The link will be created when they add their entry.
Similarly, if the Form extension is installed and activated, the user can have the opportunity to add their directory entry on the frontend using Form. This will also immediately link the WordPress user and their Connections entry.
Where this can be tricky … Form can still accept guest submissions which if a user did submit while not logged in, the user would have to login for the WordPress user and Connections entry to be linked. This confusion can be mitigated by disabling the “Submit New Entry” list action and enabling the “Add/Edit My Directory Entry” list action on the Connections : Settings admin page under the Display tab”. The later will only be shown to the user while they are logged in. The link destination will depend if Form is installed or not. If it is not, the link will take the user to the admin “My Directory Entry” profile page. If it is, it will take them to a special page on the frontend where they can add/edit their entry.
I hope that makes sense!