I've done some research about how to achieve this using various sources online. Mainly:
 

http://research.microsoft.com/en-us/um/people/yangliu/publication/tr-2008-13.pdf

http://research.microsoft.com/en-us/um/people/yangliu/publication/a%20note%20on%20planar%20hexagonal%20meshes.pdf
 

Ive written a definition that achieves this, only for surfaces that have gaussian curvature != 0. For instance if a point on a surface almost hits the 0, the definition starts doing weird things. In the papers above they solve this by 'skipping' those points on the surface that have GC = 0. This would require some scripting, unfortunatley due to time i havent been able to do this. I was hoping i would write a python script some day, (really optimistic hehe) but i dont see this happening soon.

Although there is a lot of interest in the research and definition I made so i would like to share this with you guys! Maybe with some luck we could fix these bugs and have an awesome def that achieves this!

I've also tried to achieve the same thing using kangaroo see examples below:
 

http://www.youtube.com/watch?v=wCtnkG1LVFU

http://www.youtube.com/watch?v=WaknpgMgbI4 
 

 The first one achieves planarity, the second achieves semi-planarity. As you see in the second video it sometimes gets a little unstable. Especially if you crank up the number of hexagons.
 

Ill keep you guys posted.
 

2012_PlanarHexDoubleCurvedSrf.ghx