I think it’s a mistake to assume that the best place for things like wallets and vaults is in the Browser.
For one, we want to make it sure easy to start up a vault, and have it running in the background doing it’s thing, with minimum fuss. You might want to do this on a multitude of devices and often you might want this on a device that isn’t tasked with day to day jobs like browsing. There’d also be questions around quitting/restarting the browser, or updating it and what that would mean for the continuity of running the vault. In interaction design terms we’d call a vault more of a Daemonic application, with some transient functions, whereas the browser is a sovereign application (demanding most, or all of the users attention). If we start sticking these things together we could end up with a less that ideal experience.
And regarding wallets, there is a similar conundrum. What a wallet app will be tasked with lead it to be more of a transient application, coming in an out of view for the user when required, and its functions will support use of the network across a range of different apps, not just the browser.
It’s worthwhile remembering that the browser is only one way of interacting with the network. For some users, they may have no need for a browser at all. For example if they are using a native application, like a chat app.
And of course, I can happily use the Network without the need for an account, or a wallet, or a vault, I can just browse, so it seems a bit unnecessary to have all that in the browser.
I think it’s best to think of Safe like a mini OS within an OS: an ecosystem. It’s useful for the user to have modularity. If someone makes a really great wallet app, or even better vault UI, then great! The user can install it, and reap the benefits. But if we build it all into the browser, it will get more and more bloated, and the end user may not be able to swap things in and out so easily.
That’s not to say there won’t be UI elements of things like wallets appearing in the browser, but it’d be modular, and context specific (e.g. When I’m shopping at a site, I want to see my running total in a shopping cart, against the balance of my wallet) rather than all of the possible functions of a wallet baked in.