I think you got it covered as is.
I have actually reduced the tension of the springs in the door hinge of my 9000:
it was causing the MF tray to buckle and get the image out of focus, particularly at the start of the scan when the tray is only resting on an short edge in the rails and the door is pressing down on it.
Dust is not a problem for me though, as the scanner sits in a protected area in my home office and I have floor boards, not carpets. That reduces fluff and general dust to a minimum in my case, easily taken care of by regular vac clean.
Things might be different with you. Maybe a paper or cardboard sticky tape-hinged flap to replace the door?