Any suggestions on what new aircraft will replace the proven design of the 30-40 year old museum pieces? How old you think the aircraft is that you are flying right now?
Why do you think the RAAF finding it difficult to replace the Pig and the Hercs? They have proven themselvs to be irreplacabels in many ways.
I do not think you realise the red tape and costs involved in re-engine a Cessna-Piper-Beech today. You might as well buy a brand new one of the proven design, it will cost you less i can assure you.