Fact is this is an expensive game. If they want to do it properly with a view to the long term viability and cost savings then new airframes with consecutive serial numbers are the go. You can fly them hard for at least 12 years and drag them out for a few more if need be. Not to mention in this day and age the treveling public, who are paying the bills, expect a decent level of service and quality for their money.
When you start with used airframes you invariably get differences in equipment which creates stores costs and they are half worn out before you start. Add to this the cost of finding and checking them out, forget it. New is the go.
SN