Apple would need to either replace the set top box or perfect the 'cable card'. I would love nothing more to see Apple disrupt the industry but the realist in me believes it's not going to be a easy accomplishment.
Most of us rarely use the UI that comes on the TV. Once the cable box/media streamer/gaming console. is set up the most we hit on the original remote is the A/V and volume buttons. What good is a Apple TV if it's great UI is nullified by other devices?
If a drink was enough I don't think a cellist would go out of their way to obtain a beta blocker. Most rules for cheating are reactive not proactive. The rules are set after it became known that people were using means to gain an unfair advantage over everyone else.
The big difference being that with the iPhone Apple entered into a small smartphone market, and with the iPad a almost nonexistent tablet market, but the TV set market is saturated. Can Apple make a set so vastly superior to what already exists that people will replace their current TV with Apple's?
I kind of vaguely remember reading a quote somewhere about things being legal, though I suspect that your memory about who originally wrote it is better than mine. Many or most of the people taking the drugs were not the ones it was prescribed to.