Evernote for example has a very curious feature, it is called "Annotate in image". This feature consists in that when you right-click on an image, you can click on "Annotate in image" and if you press, a small image editor opens where you can put arrows, text above, etc. (attached example image) .
For me there are three things that I would love to see Joplin do. These features are as follows:
This feature you just described, which would level up Joplin in my opinion.
OCR feature which is under development by a plugin developer (thanks a lot)
Interactive Tables (like in an excel document where you can create filter and sort options per column)
However, I do understand that my priorities may not be the most pressing issues/features that developers have/need to deal with. That is why, along with other reasons, I am trying to learn programming right now so that I can at least develop a plugin or if I can help with the programming of these features.
Note1: I am not sure about how the policy of helping to the project works. I know that plugin developers are encouraged quite a bit, but I am not sure about the actual Joplin app itself.
Note2: Please don't take what I say personal to this post. I just wanted to say how I feel about the issue and my personal view on it. Great suggestion it is.