Rabid fans all over the world are proclaiming their joy right now. It sounds like girls at a Bieber concert. Even the Apple stores are wondering why nobody showed up to buy their newly announced product.
As dramatic as PSITQ would be, I think Limitless would be the best choice. It’s part of every sub’s foundation, so if the testers suspend their current stack to devote time to Limitless, it will support both the progress they were building as well as support their future sub use once the test is over.
You could even make it a condition to pick something to work on during the test, like playing an instrument, dancing, learning a language or a job skill. Almost everybody has that one thing they’d planned on working on but never started. Making it a condition for the test may just be the push people need to get started.
Then once the test is over they not only worked on a new skill but also created a positive change in their lives that may help them improve in other areas as well.
Or am I being overly optimistic about people now? 
DarkPhilosopher wonders what he would pick. Python? Piano? Drawing? Wim Hof Method? Horizontal Mambo? 
In it’s most basic form, Total Breakdown erases all the bad stuff and builds you up better, New Beginnings confronts you with your challenges and bad stuff and forces you to deal with them, thus evolving into a more mature and hopefully wiser human being. Both are great to do. TB may deal with some stuff NB does not, NB may have results faster at the cost of being a bit heavier on you.