In order to preserve the monster trio, old trio, weak trio hierarchy straw hats need to forfeit power ups, training, common sense so they don't step out of monster trios shadow but if that hierarchy wasn't holding them down these are the power ups I think they could have gotten
1. Robin: most obvious one given Sabo could have taught her haki during the timeskip. Awakening much earlier, she's had her df since she was 8 and the government was constantly chasing her all throughout her life. At 28 she should have had awakening already
2. Franky: He could have learned to create Sea Stone in Wano and make General Franky much more indestructible plus immune to df, also he saw the blue prints for Pluton so he has knowledge of an ancient weapon
3. Usopp: most obvious one is a gun, In WCI they presented a gun that was so strong it could damage Sanjis siblings. Observation haki hasn't grown since 2014, Oda gave Usopp muscles but Usopp doesn't look much stronger, Usopp creates strong weapons for Nami but never for himself
4. Chopper: more diversity with his transformations he only uses 2 in combat when he used to use more, brain point for example
1. Robin: most obvious one given Sabo could have taught her haki during the timeskip. Awakening much earlier, she's had her df since she was 8 and the government was constantly chasing her all throughout her life. At 28 she should have had awakening already
2. Franky: He could have learned to create Sea Stone in Wano and make General Franky much more indestructible plus immune to df, also he saw the blue prints for Pluton so he has knowledge of an ancient weapon
3. Usopp: most obvious one is a gun, In WCI they presented a gun that was so strong it could damage Sanjis siblings. Observation haki hasn't grown since 2014, Oda gave Usopp muscles but Usopp doesn't look much stronger, Usopp creates strong weapons for Nami but never for himself
4. Chopper: more diversity with his transformations he only uses 2 in combat when he used to use more, brain point for example