This looks cool i agree but makign models you have to pay attention to number of small cubes your model is using. Too many of these in very common block wil llead to terrible lags. Open model file <yourmodel.json> and check how many items do you have in "elements". Normal cube is only one, while complex models in worst case may contain 100 or more small cubes. Thats why there is no way for us to have, for example, bricks model because it would lead to 1 fps in most of cities.