I don't think having a stun on a BB3 is a good idea anyway.
In an ideal scenario with Big Band you can stun an enemy using Cymbal Clash or Noise cancel, which gives you enough time for one full ground combo, after which you can do another full combo, air juggle and finisher and then (assuming you have the enemy in the far side of the arena) keep them in the air with beat extend and finish with a special and at the end of all that thow out Tuba Tuba.
All this without the enemy being able to do anything, now imagine having ANOTHER stun at the end of all that...
I'd rather they give tuba truba some other debuff, like cripple, which would benefit his tank gameplay more anyway.