You're making perfect sense. If you try to duplicate by clicking on the "New job to duplicate backup sets", it does appear that you can only select specific days. I'm not sure why it doesn't let you select an entire resource, or even all resources. I'm probably missing something there as well.
At any rate, you should be able to achieve your desired results by creating a policy that includes your daily backups, as well as a weekly duplicate job.
When you installed BE10, it should have created a template policy for a backup rotation that includes daily incrementals each night, a weekly full backup on Saturday night, and a duplicate job that runs on Sunday night and duplicates all other jobs for the week.
In your case, it sounds like you are doing full backups every night (correct me if I'm wrong on that), so you'll probably want to create a new policy, rather than trying to use the template, but it should give you an idea of how you should set things up.