I think that goku should be able to use Kaioken not as a transformation but as a move.
It would have a charge meter just like all of the other moves and the longer you hold down the fire button the more powerful he would get. However, the downside to this would be that the more he powers up the faster his health would deplete and it would automatically stop when his health drops below 10 (which is also when his powerlevel would start dropping. And I suggest that alt fire would be how he deactivates it.
It would have a charge meter just like all of the other moves and the longer you hold down the fire button the more powerful he would get. However, the downside to this would be that the more he powers up the faster his health would deplete and it would automatically stop when his health drops below 10 (which is also when his powerlevel would start dropping. And I suggest that alt fire would be how he deactivates it.