Grid Coordinates

I have had a bit of difficult time determining how to set up grid coordinates in a hex based map system, and I figure that I'll just try to fit them into a square based system relative to each home base.  This will mean that all three factions will have a completely different grid coordinate for each hex.  The picture shown above will be the grid coordinates for the green faction for example.  In this way if the world were to be rotated everyone would still have the same orientation.  This would also work if additional factions were introduced later on, as the grid would be relative to their home base even if 6 factions were participating.  I think this will make spying more difficult as everything would have to be translated.