Seriously, if browsers supported an app:// URL which just ran a local site with special privileges and allowed for some custom branding Electron would be dead overnight.
if they'd be giving you access to the complete node.js ecosystem maybe.
With electron you can easily integrate native c++ libaries for high performance stuff or things that require hardware access. It's not like electron is just a webbrowser.
You can do all the C++ fast stuff you want on the server.