IMO McDonald's wouldn't want any part of it. Their lawyers would have anything formal you put up related to these pursuits taken down just like they did that other guys' because while I'm sure they didn't like Spurlock suggesting that eating McDonald's everyday for a month ruins your health, they also don't want it suggested to the public that eating every meal McDonald's for any length of time is a "healthy" practice, or even conducive to getting a good physique, for that matter, for fear that people would sue the shit out of them after all the required long-term fat intake started resulting in heart problems for people choosing to adopt such practices.
The closest connection between McDonald's and the weightlifting world you're gonna see is the picture of the beefy Olympic weightlifter doing the barbell press pictured on the double quarter pounder with cheese box, and I'm guessing that may have been a stretch for their lawyers to ever authorize that.
McDonald's is so huge, profitable and mainstream that I don't think any of us can begin to imagine the responsibility the world puts on the shoulders of a corporation like that to be every type of "responsible" imaginable. There's a very vocal and significantly large group of people in this world that view McDonald's and huge corporations like it as basically the devil and that's getting into some heavy shit.
The closest thing we'll probably ever see to getting a fast food chain to formally advertise in bodybuilding or fitness was when Arnold got Subway to sponsor the Arnold classic a long time ago. At the '93 AC Expo they were giving away black plastic dumbbell-shaped Subway drinking cups. I don't know how many years that lasted, but if Subway won't even f**k with the bodybuilding world anymore I don't see where it'd be anything but a huge liability for McDonald's.