@tzframpton, yes, MEP Fabrication Ductwork supports flanges and joints as requested. Our recommendation at present for duct accessories would be to use the Fabrication elements such as dampers, etc, if your end goal is to produce a consolidated schedule of elements ready for Fabrication. Then, for scheduling, you can generate a schedule and other such production documents in CAMduct using the reporting functionalities.
If there are components that you are not able to produce, or output in schedules you are unable to achieve, that would be a separate request, and I invite you to create separate Revit Ideas postings provide more detail.
@Anonymous - Yes, I am sure that MEP Fabrication Ductwork does the job of incorporating real joints and flange settings. If the Job to Be Done is to have an accurate sheet metal representation that can be coordinated and can be output to CAM for production and installation, yes, these components can do that.
Regarding flow, pressure drop, etc, there are improvements that we are making to the core functionality in this regard, as indicated on our Revit Roadmap, as well as scalability and proper support for hydronic loop analysis incorporated into the 2018 release. These are to overcome challenges users have that result in various work arounds that tends to leave the model in a non-fabrication ready state. As we develop a more robust solution, we are doing so utilizing frameworks that could support Fabrication elements... but there are things we still need to do to ensure a user friendly experience before incorporating analysis onto fabrication elements.
If having pressure drop and flow to support sizing your pipe/duct networks, and associated pumps/fans is important to you, I'd recommend that you include that as a separate request here in Revit ideas.. it is on our radar, but it wouldn't hurt to see how important this is to the rest of the community via this forum.