It’s stated that each prototype changes the battle field, and we even see this happening with the stalemated kings turning to a full chessboard, the large cube planet, the checkerboarded planet, then the battlefield in it final form with those bits floating around it as the beta kids enter the session. But what would battlefields look like inbetween these 4 forms in sessions with more than 4 players?

We have no clue, the Black King Fight with the Trolls seems to imply that at 12 Prototypings, Lilly Pads started appearing on the Battlefield as well, or perhaps that was because they had already released the Grist Hoards before defeating the Black King? No idea, for all we know the Battlefield might go through various geometrical shapes until it becomes a Planet in the penultimate Prototyping, and then gets the Mobius Net on the last one.

Net which isn’t even necessary to win the game because Jade just shrank the planet itself and left it behind?

The Battlefield is just plain old weird, honestly.