Reply To: status in the calendar prior to receipt of the deposit

Yes, a second accepted status would be nice. But they’re very deep in the system and changing something on that would have to many side effects. A workaround for you could be to add a custom field with a weird name to the form with a default value. Then make it hidden with the style attribute so nobody can see it.
Then you can search for the custom fields name in the table. If the deposit is paid you delete the custom field.
In this way you can find all of the unpaid ones easily.