I know this isn't what you truly want (which many of us also want), but you can kind of get there by "sharing" things between Directory Opus and the File Open/Save dialogs using a program called Quick Access Popup (QAP). QAP integrates with DOpus and can provide shortcuts to folders you have open in DOpus.
It wouldn't hurt to take a look:
The author of QAP, Jean Lalonde (@jnllnd), is responsive on this forum. If you have questions and tag him (as I just did), I'm 100% positive he will respond. But, please do so in some other category, like Tools, so I don't get in trouble. 
There are also some scripts, like the one linked below, that might provide useful features similar to what QAP and other tools offer, if you don't want to install a "bigger" solution.