@Gorlom:
How could a Gin coverstory be too late? It can be used in the same way as Ace coverstory imo.
A perfect way to reintroduce him into the story and have him meet up with the SH as he promised.
Its sort of hard to go between "arc representation" and the way that Oda mostly does something from the recent past. Just logging through the mini-arcs, here's what I've found:
-Buggy arc: represented the "Buggy arc", returned to the story in Logue Town
-Coby/Meppo arc: represented "Morgan arc", returned to story after return to W7
-Jango arc: represented "Kuro arc", returned to story at end of Alabasta
-Hatchan arc: represented "Arlong arc", never returned to story
-Wapol arc: represented "Drum arc", never returned to story
-Ace arc: represented "early Alabasta/allies", always slightly present in story, formally returned for Banaro Island incident
-Gedatsu: tied up loose end from "Skypiea" arc with "Alabasta allies", never returned to story
-Miss Golden Week: tied up "Alabasta arc" but also used sub-part of "Little Garden arc", never returned to story
-Eneru: represented "Skypiea arc", never returned to story.
Arcs represented by mini-arcs: Morgan, Buggy, Kuro, Arlong, Baroque Works (Little Garden, Alabasta), Drum, Skypiea
Arcs with no representation at this point: Krieg/Baratie, Baroque Works (Whiskey Peak), Jaya, anything past Skypiea (Longring Longland, W7, Enies Lobby, Thriller Bark)
I somehow see precedence for a Krieg-based story but Oda just keeps going forward. And unless we get a Gin arc or an "immediate aftermath for Perona", the odds are best for the next arc to be involving someone from the World Government section. (which is anywhere between arrival on Longring Longland to the final departure from W7 with Sunny)