What are your intentions? To have very good examples of a breed and to further it by doing intentional breedings or to have a flock of chickens just to keep as a hobby cause they're cool? Or just wanting some eggs for free. Which really isn't factoring all things that went in to getting those eggsCan you give me a list of some heritage crosses?
It'd be something I'd look into.
I'm not too big a fan of the cornish X chicken. I honestly thought of getting a bunch of male Jersey Giants for meat because they're one of the bigger chicken breeds.