I posted this in a predictions thread but maybe this is a better place for discussing it. I think in the next arc, Luffy necessarily needs to have an alliance with some other power. First off, who would he fight against? Donflamingo, Kaido, Big Mom? All three of these figures have the support of HUGE armies. Before you lash out and tell me they dont…
Kidd destroyed two of Big Mam's ships. Her subordinates took it as a big deal, but im assuming two ships are not the full amount of what she owns. I am estimating that Big Mam has 5-10 ships or possibly more. Shanks has at least 20 people in his crew and I am estimating his crew to be well over 40 now. In chapter 96 you can see all the people part of Shanks' crew when mihawk visits him to talk about luffy. Later, Rockstar joins the crew and I think its safe to say hes not the only recruit Shanks has had since luffy's embark. And i know donflamingo isnt an emperor, but he is definitely in control of a large army. So with blackbeard presumably building a large army, donflamingo with a large army, big mam and shanks with at least a bigger-than-SHC army, i think its also safe to say kaido has a large army too.
So the question is, why does Luffy necessarily need to have an alliance? It hasn't been necessary so far right?
Regardless, no nation up until this point has shown internal strength that can match the power of an emperor's army. Case and point is fishman island, while having neptune's army (arguably the strongest national army we've seen yet) still needs to be under Big Mam for protection. I personally hope that oda does not take the easy road and have luffy haki 50k people again (it's only epic the first time) or have him gomu gomu no gatling 10k people (got enough during cp9). I think it would be really great to see luffy have an actual ally to fight against these huge forces that have 100m beli bounties as their fodder. So yea thats why i think it is impossible for a nation to be luffy's backup as its been for the entire series. I think the plot is set up that if the next arc does in fact put luffy against a yonkou or donflamingo, we will definitely see a real pirate alliance.