I have no idea what they changed about it, if they changed anything that is.
I do know that if they're going to stick with squirt nozzle only:
Make FLUDD charge faster, or get rid of the charge altogether, as you never had to charge it in Sunshine
Keep the charging animation cancel-able by only pressing a shield button, but remove the airdodge that follows
Increase the Knockback of the water, significantly if S4 still has Brawl like ledge snaps. Even if you used FLUDD correctly in Brawl, the ledge zones were so big that it usually didn't accomplish anything significant.
Make it do some damage; If Fludd can pump out with enough pressure to oppose gravity, I have no idea why its squirts don't hurt people
Heck, why can't the water's range be unlimited until it hits something solid like a wall or leave the lower blastzone? Water doesn't tend to just dissipate mid-flight.
More nozzles can't hurt of course. Mario can always use more recovery tricks. Fludd is a great idea for Mario and was a good idea in Brawl, but the game's mechanics just made it very difficult to be successful with. Also, they left 3/4 of Fludd's potential untapped.