I don't know if this really qualifies as a modification of TBL, but it was a little experiment that has worked for me.  I use cased-based vignettes for application exercises with MCQ's. I wanted to spur more discussion and cover a broader range of topics.  Also, I use the 25Q IF ATs for the AEs. I give them 15 questions and ask them to answer 10 of them. They end up discussing and answering all 15 questions. We get rich class discussion of all 15 questions whether a team actually used the question or not, and so far there hasn't been a question that no one has attempted to answer.  The students like it because they get to choose questions that they feel confident about, but the scores are still not 100% across the board. And I feel like it gives me the opportunity to ask more challenging questions, stuff they really have to dig through.  So, for me to be able to ask more difficult questions and they like it... that sounds like something that worked to me.