I said it in the past aswell, Weevil is major play factor for the alliance and overall wano arc.
Oda bring up Marco and the Whitebeard pirates for some reason, it will be very important for climax of the wano arc and the war against Kaido, in both way Weevil could bring two strong sides for the alliance, because that I think Luffy will face him soon.
Let say the alliance taking their L during the fire festival arc and need to retire, which means a battle/war overall in wano could happen soon. After a another L from Kaido, Luffy need a another powerup/warmup enemy to get even stronger. Weevil is perfect in that way, I believe that Weevil is at least low top tier lvl and embodies Whitebeard(Rocks arc, wouldn´t be surprise if Shiki shows up later too judging by the hints which Oda give during the flashback of Oden) which would mean that we would have a similar case as back then with the Rocks pirates.
Luffy defeating Weevil would bring such a huge impact who could chance the war in a different way.
-Luffy getting stronger by defeating a low top tier by his own(almost reaching Admiral lvl) and also probably learn something new as powerup
-Weevil changing the sides and became Luffy ally which mean the alliance would get a low top tier
-Marco and the Whitebeard pirates could join finally the war in Wano too after Luffy beat Weevil
If all these three things happen, the alliance would get a huge power for the next war, also the possibly of Navy showing up in wano would be high too.
I really looking forward for the plotstory of Weevil and the meaning what gonna be chance after Weevil probably change the sides. Also I believe it would make more sense for Luffy to take him out first before beating the first Yonkou overall, also
@Buusatan94 and many other user believe that the fire festival will end in a disaster for the alliance, so it would fit for the story overall.