I think the Seraphims' limits likely are to be shown this arc. They are still going to develop a lot. They are still children. They could come back into the story matured with haki and DF awakening for all I know. So it's not like they are written off, even if they get their fair share of ass whooping this arc.
Oda is sly: If S-hawk really has the diamond fruit, he could exploit a blatant weakness of S-hawk by for example letting him break his sword, which later on gets taken care of by Diamond fruit awakening, as in creating a diamond sword. -> portraying realistic and necessary growth.
And is no one hyped about S-bear? I want to see how folks handle pseudo teleportation and those repel paws. That fruit should still be one of the best in the verse.
Edit: Same with S-Snake's on contact petrification. Those fruits are op