The issue I have with your Kaioken rules is that there is no "check" required to use the effect. Meaning a PL1 character could hypothetically boost his stats to ungodly amounts for a round, demolish a super powerful enemy, and THEN most likely be killed due to such a huge Kaioken multiplier.
Maybe a character needs to pass a CON test (+ a Skill to increase the Pool), and must make a number of successes equal to the Kaioken level desired (3 for x3, etc). If successful, the Character would then receive, for 1 Round, a +1 to all Damage Pools and Attack Pools? I think multiplying would be a bit OP, even making it more powerful than Super Saiyan! The Ki Cost could be 5x the Level of Kaioken desired?