Access denied login form should use a node fallback

When the "PRESENT LOGIN FORM ON ACCESS DENIED (403)" option is selected, but the user is already logged in, logintoboggan outputs a standard 403 page. However, I would like to be able to output a node instead of a hard-coded text. The provided text is very user unfriendly. Since logintoboggan already preserves the previous site_403 variable, that one should be used (perhaps even exposed in the UI).