Client wants to see image alts in WP post editor, how?

Question

TinyMCE

The content is in an iframe. How to get through there and at least at the moment of mouseover to register the image in the title - alt? Then everything will be reduced to at least a hover. Or some other better solution.
Clicking on the image editing icon, where everything is, is broken for him.
upd.: It is also possible to do img with alt inside, which will always be displayed, but firstly, how to insert a script for this into the iframe, and secondly, how the editor will behave in this case