The strangler pattern of rewriting individual pieces is also what leads to 3-4 incompatible versions of Jquery. You could start with one key page and rewrite it

The strangler pattern of rewriting individual pieces is also what leads to 3-4 incompatible versions of Jquery. You could start with one key page and rewrite it in React or whatever your preference but if you never manage to kill one of the old dependencies you are just making even more of a tangled web. I would try to identify how entangled some of the dependencies are and start my rewrite with the goal of getting rid of them. But yeah I agree that version control and testing is going to be key here as you any backsliding will probably result in the idea of future refactoring being viewed negatively.