Its probably just me being wierd again but … I rarely need to dial in a new blend. So long as I know the roast depth then I know the dial setting. For example a dark roast is 04, a medium is 0.3 and a light is 0.2 on my grinders’ dial.
I’m not saying that each new bean/batch will produce a 1:2 ratio of weight in and weight out, but my doses are always 18g in and while one dark roast batch at the 0.4 grind setting may give me 36 grams of espresso and the next dark roast may give me 48 grams, it’s not such a stark difference that I would throw an espresso out.
Provided the roast depth is known and assuming that someone knows their standard grind setting for a particular roast depth, then I would have thought a 50 gram sample would be enough to get a taste.
@gotters idea gets my vote. Its gotter be a winner :-)