Auto-mapping is sort of a weird ground. It's possible (See.
https://osu.ppy.sh/s/90854) (See.
t/173380 ), but tl;dr, it would end up sucking.
Elitism aside, I could see this having a lot of issues. It sounds nice, sure, having a basis for your map when you insert and mp3, but there can be a lot of issues, such as the inability to establish breaks, slider times, differentation between sliders and notes, emphasis on certain parts of the music, hitsounding, and a lot of stuff that would make the program only mildly helpful.
Plus there's the issue that user submitted creations would become "Who put that mp3 in the editor and uploaded it"
I'd have to say a no on this one. Especially since, from my experience, peppy is sort of against automation of things like mapping (ie. A request about an auto-hitsounder got denied, as well as many other automation things ;w;)