Even if you can compile away the performance problems, how do you escape the analytical mess that is left being? Patching software the old-fashioned way is expensive because we have to integrate the changes into the model -- essentially, rethink parts of the software. But the result is certainly likely to be easier to understand down the line. In a layered, "historical" model, I now have to understand the entire history, and correctly deduce how the history has changed the functioning of the original model. That strikes me as horrible.