But the M3 grinder seems less than excellent in terms of its user-friendliness and practicality in real-world settings, as others have already noted.
I am not sure what "real world" means. The real "commercial world" or the real "home world?" Dr. Jim, who frequents these forums has pointed out to me that the design goals for a home machine should differ substantially from the design goals for a commercial machine. Indeed, many of the obstacles that we have to overcome, such as maintaining stable heat in an HX machine, are considerably reduced in a commercial shop where continuous shots are being pulled. At home, with lower usage, we're forced to "water dance and count down" in a way that would be less necessary if the machine was used commercially. It's logical enough - the machine was designed for use in a high production environment, not necessarily optimized for "the best cup of coffee possible" regardless.
I view my Versalab the same way. It's not fast enough to work in a high production environment. But it's plenty fast for the three or four double espressos I pull every morning. And it is in a whole other category in terms of grinding and distributing from the Macap that preceded it. Issues like "clumping" and getting rid of residual grounds go away.
Given the variability in basket sizes, it would be a customer-friendly touch and at the same time an homage to earlier machine designers if the ring at the bottom of the funnel were easily interchangeable with rings in different sizes (i.e. varying inner diameter to accommodate different filter baskets, 49mm, 51mm, etc.
I have successfully filled everything from a 49MM (Olympia) to a 58MM portafilter without incident. The machine maintains its excellent distribution no matter the size - its simply a matter of holding the portafilter up to the ring until the very end. As a matter of practice it isn't a problem.
If you're going to be changing grind according to the coffee of the moment, you need some frame of reference to help you dial in the location of a desired setting. I gather it's costly to engrave the face of a cone. But would it be less costly to put the markings on the top rim of the funnel? Is that a flat surface? Arabic numerals or, to honor the Italian heritage of espresso, perhaps early Etruscan/Italic glyphs ... any set of symbols with a few dots between them would do

Here I agree with you. My pencil marks definitely don't do the same thing as a scale would.

The shape of the funnels makes a scale difficult to implement. I may have a skilled machinist do it someday. But if I have to choose grind and distribution over marks - I'll gladly use the pencil.