I dont subscribe to the whole DBF thing but at least in regards to Akainu/Im, it might be easier to potentially treat New Marineford and Mariejois as possible separate arcs. Think how Amazon Lily, Impel Down and Marineford are all the same plotline but in the end, all had different (albeit temporary) antagonists for the plot they did serve.
This is how im seeing the Final War, where New Marineford is the WGs major defense against NW Pirates thinking of attacking Mariejois. We may get 2 parts of a larger war/frontlines this way, and after Luffy assaults Mariejois.
This also doesnt reallt consider BB and Shanks relevance if they survive beyond Laugh Tale, so thatll be interesting to see.