Jocly can handle anything, because basically you have to program the game yoursself in JavaScript. the standard software would not have any problem in displaying pieces that stick out of their square, at least in 3d. You would probably have to rewrite or alter some of the standard routines for chess variants; the easiest approach would be to define a multi-square piece as multiple pieces, one movable, the others just being dragged with it as a side effect.
Jocly can handle anything, because basically you have to program the game yoursself in JavaScript. the standard software would not have any problem in displaying pieces that stick out of their square, at least in 3d. You would probably have to rewrite or alter some of the standard routines for chess variants; the easiest approach would be to define a multi-square piece as multiple pieces, one movable, the others just being dragged with it as a side effect.