Yes please! I’m not a fan of wrapper apps, but for the ones that I have no choice in using (Slack for instance) it’d be great if they used the copy of WebKit included with OS X, preferably through WKWebView. While web engines are always going to be mammoths, at least OS X bundled webkit is specifically optimized for the OS and tends to be easier on the battery than Chromium-based stuff.
The thing NW.js offers is access to node.js libs through JavaScript. This isn't available through the native webview (for good reason! Very much a security risk)
Most embeddable webviews allow binding additional methods that call into native though. This is how cordova works, in fact. If you're restricting access to local html/js, it shouldnt be any different to nw/electron from a security perspective.
Edit: looks like the tint framework linked above actually isolates the webview from the node runtime. Nice.