Option 1: I think a person engaging in block-struggle against a ball, if successful he should have the advantage of gained strength (PL) from struggling and perhaps instead of swatting the ball away, having it absorbed so he doesn't lose KI or Stamina, but gains it instead; if that is not balanced enough, perhaps if the attack was particularly strong, gain a temporary raised max capacity of Ki or Stamina if absorbed (Buff. See also Alt. Buff Ideas at bottom). This is one solution to prevent having to lock the ball shooting player in position, which also seems like a major no-no because then the shooter is defenseless.
Option 2: lock the shooter in place ONLY if the victim engages in a block-struggle.
Option 3: if struggle is successful, send ball attack back to shooter with an aggressive homing lock-on.
Option 4: this one is more tedious, because you would have to treat every ball type attack differently in the game:
Generic ones cannot be block-struggled (but swatted instead); Spirit Bomb/Death Ball - the shooter is locked in place but allow the option to detonate on demand; Big Bang attack or other smaller-than-spirit-bomb ball-type attacks are the most difficult to cater for but I think they should allow the shooter to move after being shot, can't think of an appropriate drawback to this.... However, I do think that if the PL of the victim is X amount higher he should be able to swat the attack away, or if he uses turbo, reduce the amount of time he block-struggles. Perhaps apply my buff idea to the latter type of attacks?
Option 5: Idea-sex. Combine 2 or several ideas from Options 1-4 to form the final solution ^^.
Alt. Buff ideas:
Temporary increased fly/movement speed.
Temporary dismissal of Ki/Stamina depletion.
Gain 1 Shield buff/stack, making the victim invincible to the next damaging attack/combo.
Temporary increased Ki/Stamin recovery rate, perhaps even passively.
Food for thought: what if I, the shooter, shoot a ball attack and then fly faster than it to become the victim and block-struggle it myself?
Later edit:
I just got on to Discord and read the FAQ and I must say I am disappointed majorly in the direction you are taking the whole PL system. I understand where you are coming from with regards to why you have made the decisions you have, but a game should feel rewarding for playing. There is also something magical when two or more people "grow" fighting together and having a lovely battle, with rewards (gaining power, at the end of the day that is what we fight for?!). With that being said, I'm going to keep this short and sweet and say I think you are making bad decisions in order to accommodate players who are joining a server later than others. I feel you would be better off to give a new joining player the average PL of all players on the server and go from there, whilst retaining the Strength scaling of PL. Maybe turn this into a server tick option. This way, the newer player may not have worked for his PL, but he will from the moment he joins, whilst having fun and being in the same ballpark as everyone else and growing with everyone else from that point onwards. Everyone wants to get stronger in a DBZ game (PL should affect explosions range and power) and I fear you might be stripping that away. What else is there otherwise? Everyone is just going to play the fastest character to get the edge instead.