The Logitech 3D Extreme Pro has an extremely stiff spring for the roll and pitch. If you cut the top 360° and bend the top a bit to flatten out the contact at the top, this makes using the joystick less tiring.
See video below for disassembly instructions. You can remove the 4 brass screws without disassembling the stick part, with the screwdriver at a slight angle. It isn't very difficult to disassemble and reassemble. After reassembly the bottom of the stick had a bit of play, so I took it apart again and wrapped a rubber band around the base of the innards to remove this play.
The difference isn't dramatic, it seems to reduce the effort required to about a half. The stick re-centers itself as before and there is no rattle. Cutting off 1 full coil would therefore be conservative, you could go further.
The easiest option is to unscrew the 8 screws on the bottom, unscrew the 4 brass screws at an angle, remove the spring, reassemble and use 4 rubber bands to externally center the stick. This looks bad, but gives you a super low effort stick. If you need more tension, just double up the rubber.
Also, 3d printing a throttle on a cable seems like a good idea, although they want $50 for the .stl file.