I don't think he meant hotswapping in productive environments but during development. Load balancing doesn't help here.

The webapp I'm working on currently has a startup time of 50s on my macbook. If I restart the webapp 100 times a day, thats a total waiting time of 30+ minutes. Our team is 6 developers, so we loose 3h per day.

Real hotswapping may be extremely complex but IMO it would be absolutely worth the effort.