Guess I'd do a goofy league as well. Although IDP's are not really all that goofy.
I think something that would be great for that type of league would be changing around the scoring, like swapping points made for TD's with points lost for interceptions. Usually throwing TD's are 6 points and interceptions are -4 points. So just change that around to TDs= -4 points and interceptions= 6 points.