The nearest thing to what you need is Content Categories. Take a look at Dynamic User Centric Content in the Rh9 section of the RoboHelp Tour on my site.
The Employee Care sample project also ships with Rh10 so that you can see how it is set up.
The difference is that to limit the search and content, the user would have to select from a dropdown to limit what they see. I don't think anyone has come up with a way of opening the help to different categories.
The alternative would be to use merged help and have your developers call the child project for the module in the way you suggest. As a user that would annoy me because the full help would not be available, although you could create links to it.
Personally I think the best way is to open the full help at the relevant topic. The topic will be synchronised to that section of the TOC so the user can see where they are.
See www.grainge.org for RoboHelp and Authoring tips