The rewrite being cheap is about to become really disruptive.

I started rewriting the client's product and they don't even know I've started. The neat thing about software is that you can have many concurrent versions and you can keep any number of those private for however long you please. It's not something you need to make a big deal about anymore. You just put your head down for a few weeks and then it's surprise demo time. Don't even give the bastards a chance to see it coming. They'll almost certainly try to stop you given how the last attempts probably went.