This is unrealistic. Tons of "seasoned" ObjC programmers will take one or two orders of magnitude longer than an hour to write home-grown replacements for all t

This is unrealistic. Tons of "seasoned" ObjC programmers will take one or two orders of magnitude longer than an hour to write home-grown replacements for all the functional methods, and they frequently turn out limited in some way, or at least less performant. Maybe you're implicitly arguing that those developers are irrelevant to the conversation of Swift vs ObjC, and I would disagree there too. Languages need to strike a balance between catering only to the most highly experienced and specialized developers, and hobbling themselves to be "idiot proof".