I would not use asbestos as an example for comparison either of the hazards or of the mitigation. It's a different material used in different ways.
The use is irrelevant, carbon fibres once in the lung cannot be removed by the body like abestos. There have been significant changes in occupational heath over the years, even dry cutting solids containing silica wasn’t considered a hazard until recently.
I'm just going to simplify this and tell you from a position of experience that cutting carbon fiber is not a fundamental problem for a 787 freighter variant. Vacuum capture, respirators, and cleaning procedures all are demonstrated methods of controlling the risk of fiber inhalation, usually as a combination of those practices.
My current job and my last job both have been in business that produce carbon fiber products. We're actually using water jets less and mechanical machining (usually, but not always with coolant) more due to better tolerances and the range of operations possible. Manual trimming (usually with vacuuming, but without coolant) is also used to a limited degree in our normal production for cutting not feasible to do in our milling machines, as well as outside normal production such as when rework is necessary or during destructive evaluations.
I would not rate the safety culture of the previous job as remarkable, but at my current job, we have the most proactive safety culture I've seen anywhere, and very routinely create internal policies that exceed OSHA standards, where as most businesses focus on just meeting the minimum.
I have not had reason to look up all the documentation our safety team has that was used to set our airborne fiber protection practices, but from what I have seen at my current employer, I have very high confidence we have the risks very well controlled.
Therefore, I likewise have very high confidence if Boeing wants to design a 787 freighter, they can control those risks without having to deal with onerous safety challenges.
The simple fact is that mechanical trimming of composites and controlling respiratory risks from fibers liberated as a result has been done for decades now. There are precautions involved that need to be planned for when developing a production system, but they are not onerous.
Nothing to the scale of a cargo door installation in place on an aircraft. Again you are confirming my point, there are significant occupational health issues that have to be prevented. Same could be said for painting, some states eg California simply elect to ban the risk of some chemicals used in aircraft painting.
Yes, to larger
scales than cargo door installations. You can continue doubting me on this, as I'm not going to publicly state my background to explain why I am so certain about this, but I am asserting it is demonstrated practice that trimming carbon fiber on parts the size of cargo doors is viable and can be done safely.
I'm not going to make as strong of assertions about frames versus relying on lap joints, as I wouldn't know what either Boeing or Airbus has in mind for cargo doors in composite fuselages, but I strongly suspect that in a few years when we hopefully get to see pictures from inside the A350F, we'll see a frame very similar to what gets installed for aluminum fuselages.