Don't worry about E190's it will never happen ! There is no stronger airframe than the Fokker, proven in 40+ years of PNG Ops.
PX cannot afford to clean a cabin properly, let alone buy new aircraft.
Unless the Chinese government donate a fleet of E190's, you will need additional crew, to cover a transition, engineers retrained to another type, a close by Simulator, and the list goes on.
If I was a 'bean counter' I would say another F70 or F100 airframe a million $ at most, lease two engines from RR, we know they can handle volcanic ash from recent trials at Hoskins. No never-never payments so if a machine does not fly or breaks down the financial burden is minimal. Based on airframes available and fatigue life, the F70/F100 probably has another 30+ years left in them. Way to go... (from a financial perspective)