Throwing in my $0.02:
The tool mount is the part that you would want to be remixed the most, I would think. Because everyone wants the MPCNC to work for more tools.
I would just add that the mating geometry between any “universal mount” and the tool holder should be made from simple geometry (think, “not sexy”) to make that easier to CAD. It is important to balance the cost of design for something like this. Maybe I’m putting to fine a point on it. I would rather have 2x more designs available, which I think really increases the number of users, and also encourages better quality. If you had a good reason for making the design complicated, then making some sketches (you know, not just the STLs) of it would help people, without losing any protections you have on your parts.
I wonder how much you would sacrifice if you had a palm router sized cylinder mount, with another part(s) to make the DW660 fill up to the size of the cylinder. Of course, you’re fighting useable area with a bigger mount. Maybe the DW660 part could be designed in a way that would minimize the distance to the mount (an asymmetrical filler) to help with flex.