Exporting and importing should work, from a roster / franchise to a roster only. The fields that show you numbers are what the game store there ( like the head example you used - that's the ID used in game for that player's head ). Some field we don't know what they are, so any research into is much appreciated!
For the legends stances, where do you see this? I went through the player creator, wrote each one I saw down, and then mapped the values into the editor to those. If there are more we can get a list of and a roster from with those styles, I can certainly add them!