It’s always nice to wake up to an article about a new framework that embraces modularity. I dearly want to try it out in two projects of mine (a WordPress theme and a Ruby on Rails site).
One thing that I do find a bit limiting is the drop downs. It’s a dicey problem I’ve found (as a newbie to front-end development) and I want to support click menus in both desktop and mobile. Not having access to nested menus on mobile feels both good and bad; good, because the typical kind of experience is not great on a small screen, but also bad, because I feel there ought to be a way.
Thank you for including ARIA support by the way. I like a web that’s accessible, and frameworks that support it are great… but I’ll have to test how good it is in Toolkit when I have more time. 
At some point I would love to write an article about the accessibility of Bootstrap versus Foundation, and adding Toolkit to the mix is something I look forwards to.