I am asking for this feature because I want to build level in parts and is specially useful with rocks.

1) use the same model.
2) save space
3) save time
4) save load time
5) having different skins gives more power.
6) collision detection would be faster if the model involved has less polygons.
etc........

Scaling, rotating in different directions gives the impression that these are different models but saves me a lot of extra work and resources. And again save time because if one is not of proper scale or rotation then I will have to redo touches to the model.

And this has to be a wed feature and will not solve the problem any other way.