> Create an app loading screen > Use push notifications > Add offline support > Create an initial app UI to load instantly > Prompt installation to the home screen through browser-guided dialog

All of these things are possible in Safari, no? It just doesn't support ServiceWorkers?

Aside: as a web security guy I think serviceworkers are a tragedy. Any crappy site you accidentally visit and immediately hit the back button on gets 10 minutes of freebie time to execute Javascript, roam your local network, exploit "slow" browser vulns, eat your bandwidth, etc. Gone are the days when the only things running Javascript are your open tabs.