my first time around i replaced every on and grabed them later after they had leveled up on later playthroughs i kept them and on this last time have almost gotten all their key moves. and wakka with the spirt of the aurachs gains power for every aurach on the team

but if your gonna replace them heres some advice
jumal by the crystal pyler luca
zyates on the way in to the sphere center luca
ropp at rins agency on the high road
lina by macalania temple
and if you can find one a ronzo... theyre tanks

remember to save before games like if your first trying blitzball after leaving luca save before you try it. if you don't like the prizes for the league reset til you get something you like.