Image widget has got few widgets properties including imagePath. This is a generic widget and can be placed to any page content. But when applied to article template it gets the imagePath value from respective article page type field "Image".
That means when we create new article page with Article Template, the image widget will get image from article page and put it into imagePath property and with other widgets property content editor can modify that.
I have reached my limitation thinking how to achieve this as this is a difficult use case.
The solution I was thinking is in the image widget controller, check if its article page, then properties.imagePath is the image from article page image field. but then this will not work, as user might use image widget elsewheere on the article page and should get image from imagePath of the widgets property.
This has to happen only to the image widget placed to the custom article template.