So far I can see this is a bit outdated topic, but we ran into issue of version control for design. Since we're developing digital assets management solution we decided to add this functionality right into our product. Right now it allows to control versions of design files, comment over them and put visual marks over the designs. The product is integrated with Slack chat, so it delivers notifications about the comments/new versions/new files instantly. Here is page that explains about version corneal for design - https://pics.io/design
I will be happy to get comments about the feature right here or in PM.
Cheers!