I'm fairly new to AS, so please forgive me, I'm still learning!
Am I right in saying that the age of an aircraft effects bookings?
If so, I believe this to be way off line for realism. In real life I fly quite regular, using Delta/American for travel to the USA.
Easyjet and Ryanair for domestic.
My point being, If RYR for e.g parked their newest B738 next to their oldest, I doubt anyone could tell the difference. Let alone the fact they are virtually 15 years apart in age!
Maybe once on board you might think the interior has seen better days, or it looks nice and new! The point is you've already booked the flight, these factors would not have effected your decision to book in the first place.
Likewise with American etc... When I travel to the US, my flight might be on a new B777, or an aging B767 built in the 80's! These factors never effect my decision to book the flights, and like many of your good selves I am in the minority of paying PAX that would even have a clue how old the plane was.
Other factors like the ratings for a B737-300 compared to a B737-700. These aircraft are virtually impossible to tell apart for the everyday travelling PAX.
So....after all my quibbling, my suggestion would be to take the age of the aircraft out of the equation for the ORS rating.
Unless of course I've completely miss-understood it all :-)