Here are some clues about the Shimano 11-speed RD ratio. Some sources report it to be 1.4 without attribution, however…

Technical FAQ: 10/11-speed compatibility | VeloNews.com a correspondent to Zinn reports “Since I used various rear derailleurs in the past, I made the assumption that the RD-6800 would have the same cable pull ratio as the 5700 and 6700 derailleurs. But when I fitted the RD-6800, I found that, when using 10-speed shifters, it only shifted between 8.5 and 9 cogs instead of 10.”

(7.5 cog steps x 3.95 per cog) : (9 clicks x 2.3 mm per click) = 1.43:1
(8 cog steps x 3.95 per cog) : (9 clicks x 2.3 mm per click) = 1.53:1

Here are some clues about the Campagnolo 11-speed ratio. It’s listed in most tables as 1.5:1

The overall width of a Campy 10 cassette is reported to be 4.15x9=37.35 mm. The overall pull is reported, “Campy 10 shifters pull an average of 2.83mm of cable per shift, but that cable pull is not uniform. The first five shifts are only 2.5mm, the next two are 3mm and the last two are 3.5mm.” = 25.5 mm. The ratio 37.35 : 25.5 = 1.46:1

The overall width of a Campy 11 cassette is reported to be 3.76 x 10 = 37.6 mm. The overall pull is reported to be 25.9 in a post by member DaveSSS. So that’s pretty close to the same thing, 1.45:1

And that’s why I think my "Shimano-a-mano" idea should work. It would be really helpful to confirm it if someone could post the overall pull from a 4700, 5800, 6800, or 9000 brifter. This is pretty easy to measure, you can put a mark on the cable by a cable stop in high gear, and shift all the way to low and measure how far the mark has moved. Or, with internal cables, you can measure the distance from the RD stop to the pinch bolt before and after, and take the difference.