The biggest risk to Jetstar, is not coming from how hard the multiple Qantas group CEO's work.
It will be how cost are apportioned between group companies.
Jetstar's future domestic growth will be dependant upon the amount of money Singapore is willing to 'invest in/grow' Tiger. Remember in the low cost segment, he who has the lowest cost wins in the end. As for Jetstar's international ops, success will be dependant on how willing QF continues to be to support the various entities if the competition makes it difficult.
The only good thing I can see coming from this segmented business model with multiple CEO's, is that individual CEO's may want costs apportioned more realistically.
If Jane wants to pick up her kids from school, it won't be Jetstar's downfall.