I am not sure if crafting skills are going to be that meticulous in the game. If they were, it would require the handling of a lot of individual items that could be brought together to form a completely new item. This might be out of the realm of possibility for players to do because of the visual and mechanical programming needs.
That is not to say SBS couldn't implement a 3D "paint" tool that started as a 3-dimensional block of wood or stone. Using the block you could either superimpose 3D sculptures into the material and "carve" around it to create a wooden and stone statue or carving. Or, you could try to free-hand a new model that, if ascetically appealing could be saved as a new model in the game for you to superimpose or teach to others so they can do the same. At that level, however, it would be more for decoration than practical use. Still, a lot of possibilities, especially if you could scale the medium up or down.
I would like that sort of a free-form art tool in the game, but it might require SBS write its own program or borrow from a pre-existing program.