Vorta mentioned the ducting benefit on his thread, and I was familiar with it from the PC modding side of things - but basically if you put some clean flowing air between the fan and the device, you can get better efficiency.  For example, currently there are the two pillars (from the head sinks) that split the intake into effectively 3 parts - when the fan is pushing or pulling air against this, it's less effective because it's so close - less opportunity to allow adjacent air to flow around it.  This isn't technically the most accurate way to describe it, but it gets the idea across - so by adding a clean space for the air to move through, it can more easily move around those obstacles would undo turbulence.   In practical terms, if you just throw even one of my 5.6mm spacers inbetween the stock fan and the case, you'll see about a 2c drop in indicated temperature.  But once again I have to stress, the indicated temperature isn't worth a whole lot, but it is interesting.

The reason I did it was more because my pull fan would hit the screws on the back of the case, so I wanted some spacing.  I believe what I've read is that around 1 inch (for case fans) is ideal length, anything more doesn't buy you anything - but I was surprised to see such a small space made such a big difference.

As far as selling parts, when it's all said and done, if there's enough interest than I probably will... For small guys, it's a super easy mod to do, totally reversible so you can undo it if you don't like it, and it makes for a much more house-friendly S5.  For the bigger boys, I think the ducted solution will be awesome, as my hope is to eliminate the need for any fans at all on the S5's, and instead have a plenum and single large fan.  I've seen similar configurations before in manufacturing, and I spoke to an HVAC designer I know and he confirmed that it should be doable.  Greater reliability, and massive noise reduction - plus depending on how large a deployment you're doing, it probably could even save a couple amps when it's all said and done. 

One other maintenance plus of this design over the push design is that the heat sinks are exposed on the front, and if you've ever taken a fan off of an S5 that's been running for a while, all kinds of junk builds up behind the fan - and this really affects the cooling.  With the pull design, that's not something you need to worry about because it's obvious when buildup happens.