Ok how about this - give us the ability to delete the entire raid avail chart with one button so that i can ensure each week that the avail is accurate for that week when im scheduling.
Also perhaps we can import the names from the roster too so that we can easy chase down the people who are posting thier avail.
I like that idea. Provide an option configurable by the admin/operator to keep or delete the existing availability on a weekly basis. So if you configure it to delete it then every Sunday at Midnight or something similar it would drop the availability out.
Then it would make sense just at the system prompts you at login or on a refresh when your character profile hasn't been updated in a while to have it notify people that there currently haven't filled out their availability for raids.
Another sub option could be provided to users that lets them say "this is my availability and it never changes" under their account profile as some people's schedules are always the same baring vacation or emergency while others (students or part time job holders for example) don't have set schedules. In the case of the person who's schedule never changes and thus checks this option it should never delete his/her schedule. Most likely they would think it is annoying to have to fill in a new schedule every week.
edit:
or just make it prompt them the first time they login or refresh the page after Sunday at Midnight to update their availability.