We use air diverters every day in our cars. No one wants to add any more mechanical stuff in an electronic device, but it would be a way to change the air flow remotely.
The pull out the fan modules and turn them around and plug them back in would be great and easy to do.
I think the concept is a great one. However one would need to consider re-engineering the fans so that they will support bi-directional flow. The airfoils on fans today have been specifically engineered for best efficiency, maximizing air volume and maintaining a somewhat quiet level of noise at a set speed and direction. Making a bi-directional fan will have to sacrifice some of this efficiency and noise levels will increase significantly.
If we can overcome these limitations, I believe this would be adopted by all manufacturers.
There will need to be some provision for preventing misconfiguration as well. This could not be something incorporated as a configuration option but more in line with port channelization and VC setup groups.