I just think it is such a natural functionality that i've personally been missing. Im really having fun with this game creating my own fantasy factions and maps and i've found it quite a nuissance that you need to start a game just to save your custom realm/faction. But the real issue is when editing a previously created one, because even after starting the game it doesnt save to the original one, nor does it create a separate one, it only makes a temporary one for the specific match you started, therefore if you want to modify one of your realms/factions oyu better create it anew.
TLDR: To have the Create/Edit Factions and Realms sperataed form Start a Game.