The API isn't final, afaik, even after almost three years of SailfishOS. Because of it, it is a mess. Harbour apps cannot use it, so if you want to publish your app in Harbour, this method will not be accepted anyway. I wonder if Jolla still believes this is the way forward.
(everyone has an opinion) I would prefer all applications to have a common place (as originally thought by Jolla) and the settings option in the application to be able to open this panel. That is, have the same settings panel accessible from both places with the application running or not.
Most important, the settings should be backed up by the standard backup. (In Maemo you could define in the design which settings to be backed-up)