You could store UTF-8 encoded data inside the hidden bytestring. If some of the UTF-8 encoded smuggled characters are variation selector characters, you can smuggle text inside the smuggled text. Smuggled data can be nested arbitrarily deep.
Since it took me a minute to make the connection, I'll just say explicitly that I enjoyed the understated "it's turtles all the way down" joke.
To see a turtle emoji.