I'm in the process of upgrading my machine (MK3) which will include a new dust shoe. I cut mostly wood so need to keep the dust down.

I wanted to improve upon on MK2 in a number of ways, including extraction. I'm nearing completion of the machine so will post all the photos/renders soon. But in brief they are:

1. Upgrade to 100mm pipe (so it is 100mm pipe all the way from the extractor to the cutter, not throttled down to about 30mm pipe as it runs down the Z axis)

2. Floating dust shoe - the support brackets are attached to the Y axis, not the Z axis. This featured is carried over from my old machine which allowed me to set the dust shoe at just the right height, independantly of the Z axis movement. I found Z axis shoes a bit crude and can end up crushing the skirt on plunge cuts. The floating height setting is made by adjusting the collar/thumb wheel on the front guide rod. Initially the shoe drops with the Z axis but when this collar bottoms out the shoe drops no further, although the cutter can continue downward into the work.
As machining progresses the Z axis can rise and fall but the shoe stays at the same height, skimming over fixtures and creating the 'best' seal to the workpiece.

3. Automatic raising shoe - there is also an adjustable tab on the rearmost rod which catches on the Z axis if it raises past a certain height. This would be set to happen to move the shoe up and out of the way once the job is complete.

4. Magnetic main plate. The lower plate containing the skirt will be magnetically attached to the smaller plate above it on the end of the hose using recessed magnets so it can be snapped in and out to change tools, leaving lots of space for access. There are youtube links etc on these sorts of designs, and I think also some for sale (in the US?). I will make my own again. The skirt will be plastic strips which has worked well before, although you have to have enough stiffness to stop the skirt being sucked into the extractor airflow. The magnetic main plate, and smaller plate above it will both be clear plastic to give a better view of the cutting. Using snap-in skirt plates will also allow me to fit other types of skirt such as broom hair type etc. if required.

5. I'm sure I've seen commercial machines somewhere using ballscrews and steppers to raise the shoe in software as and when required (but I searched for this recently and couldn't find it so might have imagined it!). I pondered this idea but settled on the passive solution described above.

Hope this gives you some ideas. I would post a render showing some of this but having a few problems attaching images . . .