What about flexible driveshaft and water cooling both? Normal fan wouldn’t give enough pressure to blow air trough small tube. But compressed air would work. Though then you need air compressor and it would be noisy.
Water and a flex line and you might as well keep existing tech. The mass of the water in the block and hose added to the resistance to movement of the filled houses themselves added to the resistance of moving the flex line (have one from a Dremel in my hands). Plus cable management is a nightmare. Zip for them all together and you have a1 ½" bundle of tubes, water, wires and flex cables.
Electric bellows lol. I blacksmith so that is an idea i like just because. B-)
I think you will have a tough time getting enough torque through that cable without it unravelling itself. The Dremel’s flex shaft (or similar) are high speed low torque drives.
What if you run a solid shaft instead? Possibly down one of your diagonal rods(assuming you are running a delta). With some interesting gears, this could be done. If you make the shaft from carbon fibre, you might be onto a winner.
Would be great if you could embed the drive shaft inside on of the diagonal rods… 
Good luck
@David_Taylor_Gineer there is already a version of this out there working. +flex3drive uses 40:1 gear ratio. And has plastic injection gears that are only available through the flex3drive owner.
In my build I used shaft which was meant to hand drill and max 2000rpm. It doesn’t unravell at all. And when extruder itself is geared down, it needs very small amount of torque.
Okay, cool. I should maybe try this myself. Although the Bowden I have on my Delta is working just fine as it is though.
You should try it! I think this concept have great potential, but it advances pretty slow because there isn’t so many users!
With my shaft, I need to try lower gear ratio. It’s so rigid that I think 1:20 would work great!
There is a lot of friction from this so you have to make sure you don’t run too long and overheat the extension.
I just made one of those a few weeks ago! 
Works way better than my bowden.
@Tim_Blakely that looks like it’s working well! What gear ratio do you have? What is diameter of hobbed pulley?
It’s roughly a 20:1 gear ratio. I pulled the worm gears outta a set of bass guitar tuners (like $8 and you get 4x per pack). The hobbed pulley is just a standard MK7 pulley. Took a bunch of revisions to get the thing to fit on a mini kossel effector though… that thing is tiny!
I’ll ditto that the Dremel flex shaft isn’t the kind to use. I use one on a Dremel rotary tool, but wouldn’t trust it for half-day print jobs.
The dremel was just for illustration purposes. Lots of great ideas in this conversation though
I plan on trying the Dremel cable that I have