The following is recovered from a number of old threads and posted here for reference:
If you want to start proposing new aircraft programs, start with these points:
Tasks and roles to be conducted.
Aircrew training requirements.
Aircraft maintenance lifecycle.
Number of airframes required, based on your assessment of tasks.
Expected lifespan of "new" airframes, compared to expectation of available manufacturer and principal nation support.
Requirements and costs to retrain and retool all required maintenance facilities and maintainers.
Infrastructure costs to support new aircraft in all Wing locations.
As you can see, simply comparing statistics or unit costs doesn't quite scratch the surface of what you are proposing....