When playing Blitzball in FF14, every player of a Team should get teleported to their Team Lobbyroom, where the participating player can choose first which Blitzball -Role they want to play for the Match.
You can choose then between either:
Keeper > They are like Tanks, only 1 per side can be there, protects their side from receiving goals.
Offense > The frontliners with the main task to make goals, very agile.
Defense > Backliners with the main task to stop anyone making goals to thei side.
Support > Middleline which either tries to help in offens or defense, not the best in anything, but has the longest reach for passes, important to build up your play to play the ball at the right moment to the Offense.
Blitzball Roles should be Treated like Job Roles, you begin as Level 1 Beginner and gain Blitzball -Exp by doing Matches. Winning a Match gives highest Bonus Exp, but also actions in the game would give Exp, like making goals, making passes, stealing the ball from an other player from the other Team ect.
Blitzball Tournaments would be hold in leagues of every 10 Ranks of Levels, so
10, 20, 30, 40, 50, 60,70, 80 ect. or if thats too much every 20 Levels, that would be then 4 Tournaments > Beginner > Professional > Elite > Champions League
Within reaching Level 80 would you learn Blitzball Skills based on the Role you play for your Team.
Blitzball-Teams should be similarly founded like Guilds, have own names with own Team Logos. But in this case there should be no requirement of needing to have first other player just to found a Blitzball Team, every player should be able to do so, in case you have no other player to be able to play also Blitzball against NPC Teams with the help of recruited Team Members that players should be able to recruit basically everywhere wheb talking to recruitable Npcs, the player should get the option to ask them. Or to buy them eventually out of their contracts from other NPC Teams ^^
So higher your Blitzball Level, so more rewarding will naturally become the tournaments then, when you should win them, stuff like FFX based songs n housing items, more optional Team Outfit Glamours ect. , such whose are not learnable from just reaching max level. Instead you learn them from your opponents in matches if you study them while playing a match, or you learn them from findable blitzball players in futurous maps or maybe also old ones. Or you are creative in a match and suddenly invent them at a certain chance if you are lucky.
There would be also like in the Original Game then special skills. Each Player would be able to use 1 of these as their special skills (Limit Breaks) That can be anything from a very good shooting technique or passing technique to also just unique passive Abilities that can either strengthen your parameters, or add side effects to your actions in the game.