Then just put it in as a token addition, then. There's nothing unbalanced about having Goku be surrounded by a red aura when he uses a combo attack. And while it may not add anything to gameplay, it does add something to the feel of the game. The only problem I have with this and that's been being said for a long time is that only half the issue is with balancing, the rest is that they simply don't want to do it.
Which is fine if they don't, but there's just literally no reason it couldn't be implemented as a token graphic so that people would be able to go "Oh, that's what ******* Goku WOULD do!". I wouldn't imagine it would take that long to script in and there are other characters they could do similar things with. I mean, even in Budokai which is a retardedly unbalanced game, Kaioken was just a quick combo that Goku did and it left you going "**** yeAH KAIOKEN HIS AASSSSS".
Game feel. Cmon. But again, I really don't care that much I just get tired of seeing "it's unbalanced" as an excuse. Nothing is unbalanced if you just take a bit to flesh it out. One thing that I would agree with is it would make Goku seem like he has 50 moves compared to everyone elses 3, if it were a normal attack. Which is why I think his kickass 3-hit owning of raditz would be a good first or second tier attack.