It would be cool to have blindfold features.
What guarantee would there be that one's opponent is not sitting in front of a chess board? It would have to be casual-only I suppose.
No blindfold pieces means that the pieces are not shown on the board, and one has to remember which piece is where and click accordingly.
This wouldn't be too difficult to implement. Just issue a piece type with no images, a transparent empty clickable square if you will.