Does it really need to happen on one core? The platform supports webworkers and serializing certain events across channels wouldn't take much... if you look at, for example some of the cross channel rendering with react that has been experimented with, there's merit there.
For this use case, I suspect you wouldn't be able to win much with WebWorkers. You'd have to profile, but having done a lot of profiling with multithreading in several environments I've learned to expect disappointment relative to my initial lofty hopes. It feels like it ought to be easy to get linear speedups and that it ought to take something really unusual and special to slow it down; in practice you're lucky to even get "good" speedups.
