They could take a firefox approach. I think it's already somewhat built that way. Give everybody the functionality that everyone uses, and provide a way to easily (without restarting anything) add extensions for more functionality.
Actually, installing or upgrading Firefox extensions does require restarting Firefox. Mozilla has realized for a long time that this is not optimal and have a new project called Jet Pack that will give programmers a lot of control, and be a lot easier to write for, but won't require a restart. It's still in early development, though. https://jetpack.mozillalabs.com/
