I think the parent cell of a widget should have margins set to individual by default. Interior cells should remain shared.
By the way, thanks for adding the grey dot indicator for individual!
I think that belongs on how people are working with Antetype. Most times I use spacing elements to separate for example buttons instead of giving them an individual margin. In my opinion those spacer elements have some benefits when it comes to updating the spacing between elements over many screens or in regard to some responsive and wrapping issues. If the margins would be set to individual I would have to look up every instance. It would become really annoying when you forgot to set the margin to individual and already used some instances of the widget. I think you know this annoying step when you have to revert all the instances because you want your widget to share its margin properties again.