Honestly, rather than comply with a Universal Proposal that's not completely there yet, we can pursue another path to making a standard.
Standards are either agreed upon by manufacturers, or determined by popularity with consumers. Right now, the standard for playlists is "m3u", the stock mp3 playlist. One of the only barriers I see that would prevent smartlists from becoming more ubiquitous is that they cannot be exported as a stand alone file at this time. This would allow them to be freed from the application, to be burnt to data cd's, swapped w/ mp3 albums, and used to simplify the process for many.
Example- my wife doesn't want to muck around with our home PC, but likes to listen to a mix of music that is "jen approved". I created a smartlist that grabs any song with "jen" in the comment field, and plays them randomly. That list is constantly growing, and she enjoys that it is like turning on her own radio station. What she doesn't like is that she has to search for it- open up MJ, open up the playlists tree, left click Jen Smartlist once, wait for it to populate, and then either press play or double left click. The exporting of smartlists would really help to put MJ/MC over the top in terms of popularity with a feature like this- IMO, of course.