Are the bags impervious to ambient moisture?
I don't have a sack at the moment so I can't take a look (all my grain is sealed up in buckets), but isn't the top of the inner bag usually just tied off or closed with a zip-tie? That wouldn't be moisture impermeable, just resistant. I imagine that pro-breweries regularly get grains from the same suppliers, so their systems are probably dialed in to the reasonably predictable characteristics of grain from that warehouse. We're also talking about adding very little moisture, Kai suggests 2%, I usually use closer to 1%, of the grain weight. This is well within the variation among malt specifications, so you might have no problem with 10 sacks then get a sack that causes slow lautering on your system.
It's not like malt conditioning is a hair-brained idea. According to Kai's site, either malt conditioning or wet milling is used by most German breweries that use traditional lauter tuns. They seem to make some pretty decent beer.
On the other hand, mill settings, grain bill, braid quality and tun geometry all play a role. You can probably fine tune your mill to get good efficiency and fast lautering, but you still may get a sack that suddenly leads to slow runnings. Mash conditioning may help you get through that sack without readjusting your mill. Or perhaps you want to make a batch with a lot of wheat, rye or oatmeal and don't have rice hulls.
If you have a plastic braid, you should replace it, but there are variable results from different water supply braids and you might get tired of buying new braids to find a good one. I do like the larger water-heater supply line braids, which seem to be good for fast runnings.
From my experience, rectangular coolers can tend to run faster than taller, narrower coolers with less surface area. They probably help to spread out the oberteig, reducing drag.