So the best thing I could come up with (assuming a theoretical perfect implementation that wasn't horribly slow and expensive) was the idea that since many languages have their own niches and categories of problems that they are best used to express/solve, you could conceivably work on a complex problem where different parts of the computation are most elegantly expressed in different languages. So having a metalanguage that allows you to switch syntax in a lexical scope would be useful!?
Highly doubtful that this benefit would outweigh the egregious complexity cost of using a language like Autology, but a fun thought experiment.
The project was initially inspired by Dr John Sturdy's thesis "A Lisp through the Looking Glass" which is all about interpreter towers and the ability to modify them in both directions.
This is all just for fun, I've yet to think of anything truly useful you can do with this. If you have any cool ideas please let me know, they might even make it into my talk!
Highly doubtful that this benefit would outweigh the egregious complexity cost of using a language like Autology, but a fun thought experiment.