I think the point is that the urinal designer was never going to protest that the urinal was his 'art'. Duchamp called it art, and changed it from hardware into art by doing so. The equivalent would be to take something that is not a game and release it as one.
Right - he took something that wasn't art, and called it art. Like the Word example, he was taking something and putting it into another context. What about his "assisted" Readymade L.H.O.O.Q.?
Here, he took the likeness of a very famous work of art, added his own gender-bending twist (to an image of already questionable gender), gave it a clever title (the French pronunciation of the letters L.H.O.O.Q. loosely translates to "she has a hot ass"), and called it art. I feel like the video-game equivalent would be to take a very popular game, and adjust just a few things (possibly including the title) to parodize it, while bringing out a deeper meaning.
I think, with regards to the large glass, the most obvious approach would be to have a deeply allegorical game, that came with a booklet with the authors thoughts about and explanations of various facets of the game with the whole piece being the sum of both of these, not just the game alone.
Or, you could just let people think about the meanings themselves (of course, if you do that, then most people wouldn't get any meaning. To be honest, I could not figure out most of the themes in
The Large Glass without understanding the back-story behind some of the images in it. Therefore, maybe an artistic explanation is for the better). Either way, the game would provoke thought, which was one of Duchamp's main goals (he states in one of his essays that he wanted to bring art at the service of the mind). I feel as though this is a necessity for a "Duchampian" game. Even in a "Readymade" game, I feel as though it would have to contain some deeper meaning for players to contemplate. Maybe the Microsoft Word game could satirize the idea of word counts in college essays.
Also, earlier in this thread there was mentioning of Dan Flavin. His works explore a very simple (yet profound concept): The manner in which light fills a space. Here is my idea: Make a game with a completely black screen, except for some very bright areas of importance to gameplay (like ships, enemies, etc). Make all of the x-coordinates inverted (so in the x-direction, controls would also be inverted). Then, instruct players to turn off the lights in the room, and turn their computer monitors toward a blank wall. The actual game would be this fuzzy, ethereal projection (controlling might be difficult for a laptop, and moving monitors might be difficult for CRT's, though).