Upon reading the reactions from just a small number of users, it strikes me that there are some confusions regarding what would be optional and not. As far as I understand, while hiding header bar & status bar in the first post was suggested as an optional layout, the second proposal was discussing possibly non-optional layout (that's why I requested the option of tabs in caption bar). Of course, things are still under discussion, but it would lead to more constructive discussion to make it clear about what's optional and not when proposed.