I mean one simple rule would be just a hard wall at the intersections. So you‘d be playing against two players but on two independent boards and with half of the figures in each case.
Some more advanced rules could be to implement a penetration rule at the borders: you can either stay on one board against one neighbor or jump over to attack the other neighbor.
Yeah, you're on the right track, but I see three partially superimposed boards...
You are actually closer to the truth than I thought...
There are only contiguous paths for half of each board with half of each neighbor...
But I could imagine a "space warp" for the other half to either neighbor...
Could possibly be modeled with three separate chess games running simultaneously on three boards but only three armies... And at each move, you decide with whom you are interacting and which board is in play...
