We were in fact discussing about using maths and images in drop down lists many years ago when most people still had IE that was only able to use text in drop down lists. I made some demos (in moodle 1.9) about javascript (jquery) based workarounds - how to create similar kind of elements that were not actually drop down lists but div elements and used in a same way as drop down lists in one of my editor demo plugins.
Exactly a year ago I noticed that since moodle was using Bootstrap already (in themes) and jQuery was not "so banned" anymore I made a new post about this topic:
https://moodle.org/mod/forum/discuss.php?d=253520
Tim's response was: "Why just give students a pre-defined list of possible options. Let them type there response like STACK does."
Type - LaTeX.
So I decided to delete those demos and my whole test server http://korpelainen.net last year...
You can still use images and mathematical notations (and equation editor) in many standard question types and OU question types - one of my favourites is Drag and Drop Matching question type