Phil,
You need to look at statistical probabilities.
Training needs to be realistic not unrealistic.
Having multiple emergencies at altitude is in my opinion unhelpful, it just becomes an exercise in running through the checklists and determining in which order they should be run.
We manage to do a lot of negative training in simulators.
How often have you done a RTO or EFATO in the box at what could be considered a "training weight". I would rather see people demonstrate an RTO or EFATO at limit weight, see what effect not lining up within the line up allowance makes on a limited runway, let them see the GPWS go off on a close in obstacle because you are only going to clear it at 35+ feet.
I think that these sorts of exercises will make people think more than having multiple failures enroute - but that is just me!