That's all well and good but how many lines on a P Chart?
Factored or unfactored?
I would suggest about the best you could manage would be an excel spreadsheet with %s added for each 1000' above MSL, each 1 degree of slope, each 5 kts of HWC etc. and then a final buffer % added at the end.
But you would have to sit down with the actual charts and calculate all exactly what % each of these things adds to the basic zero wind, level, short dry grass MSL strip.
Personally I believe the variation in airfields within Australia is so small you'd be better placed simply working out a MTOW distance for several sets of circumstances and just eyeball it after that.
Unless a purely accedemic excercise I think you're on a flogging to nowhere
