It was suggested by Leo Davidson that I post here about my tool, ExQueues. An information page is located at shellqueue.sourceforge.net but basically it is a GPL application that works with Directory Opus (and Windows Explorer). It allows a user to 'queue up' a bunch of file operations for sequential processing, with some built-in features for certain file types. File operations may be queued up at any time, and may be reordered. Processing them sequentially reduces system resources (memory and disk thrashing).
In particular, this application is useful for large or multiple PAR2 (Quickpar) based repair operations, and RAR extractions.
Drag and Drop is supported in Directory Opus through the use of the DDE interface in DO. Instructions can be found at the url linked above. Context menus are also supported by right clicking.
Hope someone finds this useful, or that someday a similar feature makes it into Directory Opus built-in.