Don't know whether this will work, but the HF impeller can be replaced with a Rikon impeller for a big improvement in air flow.
On the filter, Grizzly at least has one with a cranked flapper that knocks dust off the inside of the filter. Not cheap, but I think I'd prefer it to the Wynn steel filter I have now. Makes it simple to clear the filter with no fuss. Walk by, give it a few cranks, improve performance. Easy Peasy.
One last thing for me, I agree with gluing a little peep hole cover into the wall of the can.
The more I do, the less I accomplish.