Device Specific Layouts
I think it would make a lot of sense to have an option to toggle between device layouts/designs (Desktop, Tablet, Mobile).
Each one would have it's own Design/Prototype and Share Modes with each one having it's own Assets Panel, which could be synced between all of them, if the user wanted.
With this, we could personalize and greatly organize all the assets, styles, etc. into all the devices we wanted to design.
If the user didn't want to design for web/devices, it would have an option to define which type of design he/she wanted.
João Marcos commented
I imagine it like this! (image attached)
The user has the ability to toggle between devices and each one has it's own assets (with a possibility to sync all assets between devices - to try to escape design errors or mismatch of assets).