Worst scenario?
Ah well, it springs to mind instantly.
Giving a check in an L10 sim long ago, the new (to the company) pilot says...Well, in Germany, when we go around, we push (the throttle...way up) then we pull, (the pole....way back) and he does so, whereupon the sim jacks extend fully with the cab at a 45 degree angle, and it stops.
Dead stop...no more motion.
Then the power goes off.
We exit down the rope, just as the Halon goes off.
This ain't nice, and I don't recommend it to anybody.
Now, as for reasonable flows during the exercises, keep it completely reasonable and proper, and positively don't introduce too may 'failures' all at once.
Unreasonable excess failures, quite frankly, prove nothing, and does NOT induce a learning environment.