There are common rules for games in general, so there is a huge objective part in that.
Ask yourself the question, what this full scale galaxy adds to ED?
It's an interesting thought.
Try to imagine a game like WoW or ESO.
Take out the storylines, overarching quests and long term narrative, explicit MP content like raids and group dungeons and factional conflict and replace it with fetch, delivery, kill quests plus some resource gathering.
Now add a few hundred million square miles of empty landscape, rivers, mountains, woods, plains and lakes around the populated game world.
Throw in 35 or so customizable mounts, and voila, you'd have planet based ED.