The simple answer is "yes" - the more complex answer is "I think you should be able to do this without MetaMod".

Using the normal Menu Manager, you should be able to assign modules to the menu item that DocMan appears on. If you don't have a menu item for DocMan, then you could just make one. If you don't want it to appear on a visible menu, just make a brand new menu and add DocMan as an item on that menu - but don't publish a module for that menu, so you won't get to see it in a menu on the page.

Can you make it work that way?

If not, then it's easy to do in MetaMod:

if ($option == "com_docman") return "XXX,YYY,ZZZ";
// replace XXX, YYY and ZZZ with module ids to return when viewing things in the docman component.

Cheers,
Stephen