I've been curious about this topic for a while and it led me here.  All I know is that in KH2 Final Mix, we have a rematch with Lexaeus and his power officially goes up to as high as 100,000 (technically 99,999 but close enough).  So I'm using him to scale powers based on how the fights seemed to play out in the cutscenes and character progression.  I have some rough ideas for the Organization members as of right now: 
Xion: 125,000 
Roxas: 130,000 (358/2)- 160,000 (kh2) 
Larxene: 107,500 
Marluxia: base-120,000 second phase-160,000 final form-200,000 
 Luxord: 90,000 
Demyx: 87,500 
Axel: 115,000 (358/2-COM) 145,000 (kh2) 
Saix: 157,500 (moon power-195,000) 
Zexion: 105,000 
Lexaeus: 100,000 
Vexen: 81,500 
Xaldin: 117,500 
Xigbar: 155,000 (Braig: 140,250) 
Xemnas: base-225,000 armor form-290,000 final form-350,000 
Ansem (Xehanort's Heartless): base-95,000 final form-145,000 
Twilight Thorn: 45,000