Lisps have had this for decades. The realization that one could do this was one of the things that killed lisp machines, since it enabled lisps to be implemented efficiently on stock microprocessors, which were much cheaper due to economies of scale.

In SBCL, this also allows cons cells to have their own offset, so car and cdr are implemented with one instruction and are safe (that is, throw an exception if applied to something they don't work on) even in code compiled at (safety 0).

Now just waiting for parallel GC in SBCL. ;) Well, also waiting for some other things, I will admit.