There isn’t a way today, but it’s an interesting idea.
There is some complexity for us because we don’t ship MP3/AAC codecs (because of patent licensing complexities)–so we are to some extent stuck with what the OS provides for us. I’m not sure offhand whether each of those codecs has this capability or not.
For AAC, I believe I’ve seen decoder implementations that can decode to a higher bit depth. I’ve not come across that for MP3 but that doesn’t mean it doesn’t exist.
Do you know of another player that is doing this? Meaning–actually producing 24bits that isn’t just zero-padded 16bit output from lossy files? I’d like to poke around.