My brother has been looking for a lego design for a chess set. This is the first i've seen and looks very doable. One suggestion though. I would use crazy glue on the pieces so that they don't come apart as you play.
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Another thing you might want to look at (something i realised when we were planning to make a lego chess) this could kind of serve as a travel chess but without the magents, so you might want to try to design some kind of baord that closes and stores the pieces. Just an idea.