Reform is the Refactor of politics. Don't underestimate the value of all the details figured out in the current implementation. And never stop refactoring if you don't want to end up in a huge mess where ever further step is a pain.
Rewrite is the Revolution of building software. As we learn from history, revolutions more often than not ended with even uglier powers taking over. Be clear what the new system looks like before you throw the old out the window.