Do you mean it is 'uncomfortable' for teachers to set a topic based format? (Theme in Moodle is usually used to refer to the look and feel of the site).
OK - I'm not sure why that would be the case, For me I have always preferred formats where I can set a title myself rather than date based, but that is I guess personal choice.
Maybe there is an opportunity for someone to extend the Weeks course format with an option to set the time period - daily, weekly, 2weekly, monthly etc.
As for the grade report - well that would entirely depend on the gradable activities
set. One section may have several, while another may have none at all. Grading isn't tied to course sections
at all, its tied to the separate actvities that may or may not be within a section. So, a better solution may be to extend the grade report to include the date of the activity rather than the section its in on its course?