Electronic board game - Blood Bowl clone

Some interesting developments over the last few evenings as we've put together all kinds of ideas for an intelligent board for a board game (like, our old favourite Blood Bowl).
Our original proposal - based on freeing up as many pins as possible from two 40-pin PIC microcontrollers - was to allow for up to 600 squares, or a grid of 20x30

To allow for as much flexibility as possible, while at the same time making it relatively easy to understand, we've decided on a modular approach. Our board game will actually be made up of a grid of 4x2 "blocks" which can then be wired together in any arrangement. It means we've lost the flexibility of really wacky board layouts (although using the same technology it should be possible to create one-off boards with pretty much any layout as required) but does mean that we can simplify making boards of different dimensions.
(it also means that anyone who buys their copper boards in eurocard 100mmx160mm size can still make a board game, using a "patchwork" of smaller boards)

4x2 Board Piece

Each playing square in this board is marked out by a "cross" shape on the board. Small through-hole studs are soldered to this underside, so that on the playing side of the board, a small contact point is visible on the playing surface. Each playing piece has a conductive base (a copper coin glued to the bottom would suffice!) and when placed over the four points of a cross, makes a connection between the top and right contacts and the bottom/left contacts.

Using the above layout, we can place these pieces side-by-side and join the edges, while connecting each group of top/right contacts together using short pieces of (insulated) wire

Using this approach, we've designed our Blood Bowl board.
It's not quite 30 x 20, but we found that vertically connecting 7 "rows" of 4 contacts means for each row we can read back up to 28 lines of "column" data. By placing four of these smaller boards side-by-side, our board size is 28 x 16 playing squares. Not a bad compromise and certainly a sizeable playing area for a lot of different board games.

So what does it look like? In short, a nightmare!

As you can see, each smaller board is connected to the board horizontally next to it (the traces were deliberately lined up to make this bit quite easy). Every 7 vertical rows of contacts are connected via wire traces (shown in this diagram by different coloured bars) and each group of these 7x4 = 28 contacts is then connected to the slave microcontroller via a short wire (the connection points for these wires are circled in a matching colour).

There are 16 wire connect points - these go to the master PIC. The 28 traces from the bottom/left sets of contact points are connected to the slave. By flashing one of the 16 wires at a time, and reading the input values on the 28 inputs, we should be able to work out which set(s) of contacts are being bridged by a playing piece on the board.

That's the theory anyway.......