I want to enable extensions to run as PWAs

Extensions make for a great sandbox to protect users. This is extremely important in financial applications where the safety of websites isn't sufficient—notably the risk of a DNS attack (hacker reroutes your URL to a different domain)—and can cause users to loose a lot of money. This is even more important in blockchain applications because theft of funds is irreversible. This has actually happened multiple times—the most notable being MyEtherWallet getting DNS swapped
.

To avoid DNS swapping, MyEtherWallet has a Chrome Extension version of their website and also allow you to download their website as a PWA. Many other cryptocurrency wallets also publish Chrome extensions for the same reason.
Companies that don't want to open up the risk of running as a public website can't leverage all the benefits of a PWA because they don’t exist on the web. Additionally, many users perceive native desktop apps as more secure than Extensions. Being able to have a PWA would allow these companies to ship a desktop client without code modification or loss of security.

Since browser extensions (with manifest v3) leverage Service Workers, the architecture is very similar to PWAs. It feels like developers should be able to submit their extension and toggle an “Install as a PWA” (or similar) option.