anything is possible
I would have to modify the mpscan plugin to generate a special xml file, but I find this command tends to be overkill. It takes a lot of memory, especially if you also use the regular play song command, which is already pretty demanding. I wonder if anyone really uses these commands once they get them set up... It seems to me that if you have multiple songs by the same name and you get the wrong one, you can just skip to the next track, no?
There are other ways to accomplish this too, using what is already available, but they are slightly less reliable. That is, you could request a song first, and then after that command you could specify the artist, but it would still be listening for the list of all artists, not just the ones that play the current song.