That sounds like a good solution. I don't want to need an account on a different platform to see Threads, but I also don't want the feeds to just be overrun by Threads users, and that seems to achieve that.
I guess the ideal situation as far as I'm concerned would be for users to be able to choose that setting on an individual basis. Obviously anyone can set up their own instance and achieve that, but being able to do it without being an instance admin would be the best.