such a mechanism wouldn't be able to guarantee 1g accuracy, not even mentioning 0.1g. What if you end up with more beans that you want? say the doser dispenses 2g more, then what? how do you get rid of the excess 2g?
I don't see why? It should be possible design doser vanes or something similar to Versalab hopper that allows you to drop beans from the hopper with the accuracy of a single bean, without making it awkward.
And of course the scale part of the hopper should be open so that picking a bean or two is possible in case you overdosed and want to get it exactly right.
Regarding dosing whole beans vs grounds: whole beans have a slightly smaller maximum accuracy, but a lot of people happily rely on methods that are significantly more imprecise in terms of weight. I have hard time believing that accuracy of a single bean was not enough for (nearly) everyone.
You need a mechanism that can weigh the ground beans on the fly, some sort of horizontal scanning or a very precise dispenser for ground beans. Of course you would have to grind more than you want, dispense precisely the amount you want and get rid of the rest.
From my point of view, these kind of "coffee management issues" should be tackled in the stage where coffee is easy to handle: whole beans. Grounds are a lot more difficult to manouver, go stale etc.