What else will you abstract? Just abstracting login is not enough to justify this. Login is easy with bunkers and something like window.nostr.js.

Or even if you don't think it is, that's the same thing the Spring browser tried to do, and you could do it on a platform by rehosting web clients and force-including a window.nostr global that implements NIP-07 even for people that do not have an extension, and done.

But why?

I think it could be more interesting if you done something different like abstracting the UI and providing all apps with a homogeneous theme, or doing what I said on the note above, or perhaps also abstracting relay pooling, connection and selection and smart relay picking on behalf of apps, I don't know.