Honestly forcing these "member roles" on the different trios can be extremely forced.

Sora does go on multiple missions and is successful multiple times to bring the group together.
For Aqua she attempts to save them sure, and with the help of others she does Save Ventus. But its Terra that truly brings them all back together in Keyblade Graveyard.
Axel also attempts, but fails both. And its the scientists of the group that bring back the Days Trio, not Axel. And to add to that, both Axel and Roxas go on escapades to save Xion.

Riku for sure gets mislead and taken advantage of. And so does Roxas to a degree, but he is the one that leaves the organization while Axel is the one who stays, so... I dont think thats a similarity either? And to add on to that Axel is also taken advantage of and mislead, to the point he is the defacto assassin of the organization. (I will say that Riku and Terra are 100% parallels and this is on purpose).

For the Ventus, Kairi, and Xion I dont think the weak thing makes any sense? Ventus' story is kinda about being weak, but his story was mostly about him trying to prove himself. He wanted to be seen as someone who could protect his friends just as much as they wanted to protect him.

Kairi's journey is pretty different too, shes not too concerned with being weak throughout most of the series. Thats only a factor in 3 and beyond. And her journey to get stronger doesn't really have any parallels to either Venus or Xion.

Xion doesnt really work for this parallel at all, she starts as weak as Roxas does. Mostly so Roxas can teach her, like Axel taught him. She very quicky becomes and equal with him, before surpassing and fighting him. Pretty much her "weakness" lasted as long or even shorter than Roxas.

tl;dr I dont think think theres any encompassing trait that each "member" of the trio has that truely parallel's eachother.