Well, it wouldn't be too hard to program - you could just draw all of your sprites at 3 times the size you want them to be, and then have the code separate it into blocks of 3x3 pixels and work out which of the three columns are filled. It would then generate the subpixel sprite using the colours necessary to create those 'columns.'
If the images you put into it featured broken columns - if you don't know what I mean I'll upload an image to demonstrate later - it could either just treat columns as empty unless 2/3 pixels are 'used,' or adjust the brightness of that column accordingly.
Whether or not it would look any good is another matter entirely
I'm not sure that I'll have the time, either... I'm studying for my exams at the minute, and doing a ridiculous amount of work for art, and I need to finish Infinite Afro, too. Actually, my exams finish a month or so before the deadline, so it should be okay. Who knows. It would be cool if someone made a game like that, though