How could you isolate apps in service worker?
Are you going to provide fake localStorage and indexedDB?
Fake localStorage is relative easy, but indexedDB has a large of api.
(as I said in Are there any Webxdc runtime which works directly in browser? - #3 by gholk )
In my opinion, the runtime should be able to export the save data, so user can move apps and data to other devices.
It is also easy for localStorage and hard for indexedDB.
I am interested in how will you deal with these.