I think it’s definitely worth considering something like this for core… one thing I’m not convinced on is having the hamburger icon on the top left. I don’t have a particularly large phone, and it’s impossible for me to reach that top left corner with one hand (the top right is pretty far away too, but it’s at least possible). Swiping helps, but we’ve also got the native browser gestures to compete with.
Also for what it’s worth, it’s starting to feel like more apps are beginning to move away from the top-left hamburger menu on mobile in favor of the bottom bar. (For example: Google’s new News app and the latest Netflix redesign have their primary navigation links in the bottom tab bar.) Bottom tab nav is a whole different conversation (and we’ve got a nice plugin already!).
One of the trickier things in the hamburger menu is how we handle categories. I think the flat list is starting to be a bit limiting for sites with long category lists, and it’s not particularly well suited for subcategories. Should we limit to popular categories (globally popular, then personally popular?) and rely on the full category page for the list of everything?