If the only way to implement Blitzball in this game, is to make it another Squadron like thing..well maybe its simply not for this game and the time to create that should be used for different content. IMO not every single Mini Game from other FF should be in this if it does not go well with the game itself. You will just have another rage coming to you. If a match is truly quite long (I dont know Blitzball that much) then yes its probably too long for an MMO (TT does have short games) especially if you put another grind behind it. IMO a mini game should not be something that you need the most of your time to do it good..it should be something that you can do in between stuff that will be used as a bit of a break from all the other content in this game. LoV failed (IMO) because it was way too complicated for a mini game. Simple one vs one battles between NPCs or players and a way to train them would have been enough.
So if Blitzball in any way takes too long and is complicated or boring..then you will truly just have another LoV..thats why I dont understand why its even necessary to be in this game.
About rival wings:
It seems that its still a bit more used on the japanese servers. At least thats what some reddit users wrote. So again it seems that they love to look at the japenese market and not the rest of the world..or they truly just take the first few weeks and see it as a success if its used there..which would just be really bad.