I tried designing my own nozzle inspired by Darko's prototype. Here is a cutaway view of the nozzle. I printed it out and tested it but it has two major flaws.
With the nozzle being printed tip down the hole spacing is compromised a bit by the elephants foot on the first layer. I could overcome that by making the holes even larger to compensate, but that is not very portable.
More importantly the air flow is fairly unfocused, not nearly as efficient as with a single 2mm hole. This could be improved a bit by elevating the inner wall 1 mm above the outlet, allowing for the outer wall to be brought in a bit. The down side is the more we do this the more air will tend to flow back up the inner hole. Also we would need to print this in a different orientation. Printing it on its side would probably mess up the nozzle, we need it to be very uniform so the air flows straight down. So we would need to print it upside down, but that would involve a lot of supports or we would need to drop the top of the barrier.
This would all be simpler if Cura would print single line walls, that would allow us to make the inner wall half as thick. However for some reason the default is to not print thin walls.