Allow to page script/part switch into local mode. This mode will be created to growing market of web apps. Some apps needs to further integrate with system, such like loading data/files. In this mode, application may read files, but has no way to communicate with network and other parts of page. It cannot write files, but to Indexeddb and all data written in this mode could be accessed again only after switching to this mode. There is no way to exit from that mode, but reset script/part of page (to ensure security).
Another usage is web help. This idea was born, because KDE team refreshing one's user base. I was thinking, how improve user experience and figured out, we can do not put screenshots, but load real Qt/Webassembly apps. Such apps will read desktop settings, such like wallpaper, color scheme, style, icons, etc. But we must enhance the security.
Imagine - MS, KDE and others could drop static images with screenshots and made it autogenerated by browser, based on user preferences. And, of course, some app, like Photoshop Web, etc. could be enhanced too. It could load images from hard drive, list files on it, but cannot write anything without permission. But... Photoshop Web (for example), could also read desktop settings, theme, etc.