We can kinda have that already, it's just non-standard and rarely used. Here's for instance neofetch with actual graphics:

https://i.imgur.com/fHdkkLn.png

If your terminal exposes an API screen readers could access, there's nothing stopping it from defining escapes to allow you to assign aria roles, etc. to spans of text.

But there's a bit of a chicken and egg problem there - you need a terminal to expose it, and a screen reader to support it before there's any benefit for any applications in adding it.

One way of pushing some support for that, though, might be that if terminal apps annotates their output, it also opens the door for selectively letting users override presentation of it.