Regarding our MC, it feels like he will hit a growth plateau if after beating a B+ he feels dwarfed by an A.
I don't know of there are many levels to S, but the island mentionned last ep seems to be difficult for all S hunters we've seen so far.
Also, there's an S that will soon come after MC.
We've heard a lot about a second awakening. I guess that's what will happen at some point, he'll get quest to improve his base status.
Maybe directly to S, or gradually.
Also, we have no idea if he's the only player.
If he isn't, a S hunter getting into the same process would be either a great ally, or a tough opponent.
If such a player exist, she could be that blonde. Too much screen time when she feels like a background character.
Lastly, what about the growth of that B healer? When is it she becomes useful to the story or just becomes irrelevant and stops spoiling frames? Even that C-hunter has more meaning in less frames...