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