Fewer pins = better?

 The idea of losing the data wire, and requiring only power and ground to make our board sections work feels almost revolutionary! Suddenly, we could have board sections on top of buildings (for large, open area wargame type scenarios). But reducing our connectors down to just two pins (instead of three) also means a slight problem - because a two-pin connector isn't symmetrical.

And, as we've already discussed, having boards with just two pins can mean all kinds of problems if someone were to rotate the board around, and try to connect incompatible pins together

And the answer was as simple as it was obvious.
Simply stop trying to make the board panels symmetrical! Don't allow people to rotate the boards to connect them together!

In fact, making the board panels in such a way that they could be rotated only means additional complexity in working out where each square on the board is, in physical space.

As the board piece rotates, the physical location in space of our 0,0 origin square moves (as does every other square on the grid). So if we allow users to place their board panels in any orientation they like, at some point we're going to have to discover this orientation, then apply a series of offsets to compensate for this rotation, when accepting inputs from the playing surface.

If we received a signal that the player had just put a piece down on board number 1, at position 0,0.... well this could put the piece in any of four different physical locations, depending on which way around the board was rotated. Is it in the bottom left of the board? Top left, top right or bottom right?

The obvious answer is to simply force the board pieces to connect in only one orientation.
And that's as easy as offsetting the connection pins:

Suddenly, we've got a really flexible playing surface - you can add batteries and make each 4x4 "panel" completely portable (if required). But you can also "daisy-chain" multiple panels to make a much larger playing area - and we've got a way of ensuring that all panels are facing the same orientation (which makes translating board square references into real-world space much easier!).