Interesting info on oil choices:
IEC 60422, IEC 60296 (Google search should turn up some useful links) and

http://www.power-eng.com/whitepapers/2012/shell.whitepaperpdf.render.pdf

I think oil and cubes design could be integrated. If you couple the heated oil to water, you can generate hot water and save on that as well. Some ideas to ponder from the world of power transformers http://www.electrical4u.com/transformer-cooling-system-and-methods/

Not to be contentious, but Sebastian I think you are mistaken regarding the operation of equipment 24/7. Intel and many other data centers have done exactly that. Intel did a one year pilot study and follow up failure analysis indicated nothing of mention. There are certainly other issues in terms of maintenance, which is where good design can make a significant difference. Modular mining units (the blade designs appeal too for this reason) that have snap on feature seem like a good idea IMHO. If you search for the Intel pilot study, it is also interesting to note the significant decrease in power consumption. Considering that these miners will have a carbon footprint the likes of Godzilla rampaging through downtown Tokyo, this is a good thing *financially* for miners as well. Less cost up front.

That being said, there is the oil and despite the videos demonstrating ease of service http://www.youtube.com/watch?v=U5zoIEjo1Zk there's still the oil. The fewer small parts to drop, misplace, recover from the bottom of the oil reservoir, the better.

Lots of design opportunities here... I don't think ordering a GRCooling Carnojet system is necessarily the most prudent solution for everyone... as pointed out previously the shipping costs are likely crippling.