You can do this now in Webflow using Firebase as a backend… just a thought… so it is already possible to do this editing of webflow content inline, on a site hosted on webflow server.
Another possibility, if you want to host the sites you make with webflow on your own servers or your clients own servers, is to use a service like Surreal CMS or Pagelime CMS, which let you assign class names to items to make them editable, and then your clients can log into the online CMS of choice, and edit pages that way too.
I prefer Firebase, so that sites can be still hosted with webflow, and not have to deal with moving sites around to different servers etc. Regarding Sketch, it is a great tool. I agree with you, webflow is the best tool out there and most fun to use
From the experience that I have had while making the library though, the coding aspect of it, is no more complicated than say coding php for wordpress templates.
Firebase was acquired by Google and is part of their suite of cloud services. Firebase is basically a NoSQL cloud database, basically storing data as JSON with key/value pairs. What’s great is that you can do everything client side. Apart from storing data through client end code Firebase also provides Authentication.
So now imagine, Webflow, with all it’s great features, but with the ability to have user logins and a user area. This pretty much would be killer, but is a lot more technical to implement, and a little technical to make sure your code is secure. You can see some firebase auth documentation here https://firebase.google.com/docs/auth/web/manage-users .