Ramzy spoke about this in a situational recently. Some key points:
Purdue's punishment for sucking every year equals the reward for winning the Big Ten.
So instead of relegation, have the B1G doormat over a three-year aggregate forfeit a percentage of its BTN winnings each year to the other schools. Call it the Suck Tax. There's simply no carrot anymore for improvement in the Big Ten with all of that money guaranteed.