I've got one that basically works on the same principle, you might be interested in seeing the adjustable fence, it's pretty simple.
I swear that my american (m&r style) auto squeegees lay flat without a jig as do my plain wooden manual squeegees. I haven't used it yet since it needs a new wheel, but they're only 20 bones so i should get on that..
I'd be interested to see the fence any other suggestions to make thus better...I've never seen a commercial sharpener in person.
I need to clean it off, the desire hasn't been there because the wheel is dull, but now that I figured out that I can use glass grinding wheels I better get to it.
As you can see; at the top, there are holes to place one end of the fence to make major adjustments and then theres a threaded rod to make minor adjustments.
As for how the M&R style holders fit
The carriage bolts basically keep it level, but it would probably be in my interest to make a jig.
This is my favorite holder, this is a thieme style squeegee.