How is kaioken any different than turbo, except for it being a unique boost to Goku?
If Kaioken were to be "added",it would need something more than a cooldown/timeout period of a minute to balance it. I'm thinking that it would A) replace Goku's turbo, but provide a boost in pl somewhat higher than normal turbo, and to counteract that B) it would drain from the ki, stamina, and health bars at varying rates, and these rates would depend on what level you were currently using.
Ex. Base Kaioken
HP: -1% of total max hp per second
Ki: -3% of total max ki per second
Sta: -10% of total max stamina per second
whereas
Kaioken x4
HP: -8% of total max hp per second
Ki: -12% of total max ki per second
Sta: -20% of total max stamina per second
It might also be restricted to use in normal form, or if its used in SSJ form, the penalties are higher because of his already high powerlevel being further enhanced by use of kaioken/super kaioken.
Or the team could just give Goku a red aura to shut ppl up >_>