You are right to a point, P4P means judging a fighter on how great their skills are and how they would carry over into a different weight class.
However this does almost always result in the lighter fighters being classed as better, they're faster, more agile etc etc so obviously skills alone, their bodies are more capable to execute slicker boxing moves ........ but then at the same time that's completely discounting the power and size of the CW's / HW's which make all the difference.
If you were going to use "P4P" I'd of said someone like Roy Jones was a good example, and he proved it by using his abilities at HW.