Bills gets his soul stolen
Why would soul stealing kill him? If all the soul stealing technique does is steal souls, it stands to reason that Bills's body and brain would remain unharmed. How will soul stealing prevent his body and mind from killing Galaxia?
Just because if someone's soul is stolen in sailor moon universe they die, it doesn't mean that the same is necessarily applicable in dbz universe. Souls don't necessarily work the same across all universes.
It really could go either way at this point.
Souls/spirits exist in Z. When they are out of the body, the individual is dead. That's in all fiction that involve souls unless the individual has specific resistance to it, or has no soul like Blackheart. You could just as easily say chi wouldn't have the same effect in cross verses.
Correct. Chi quite possibly will not have the same effect in other verses. Galaxia's Chi might work very differently than Goku or Vegeta's Chi. In fact, this is CONFIRMED in DBZ when Goku asks Bills why Bills is invisible to Chi sensing and Bills replies that his chi is "Godly" Chi which is why Goku cannot sense it.
The reason why Bills would still be able to blast Galaxia is because his blasts don't involve any of Galaxia's chi. It doesnt matter if HER chi works differently, as long as his own chi works properly. If Bills had some sort of Chi stealing ability, I would totally agree that it might not work on Galaxia.
Galaxia's soul steal however relies on the assumption that taking Bills's soul would instantly kill him. As they are from different stories we can't just assume that souls work the same. If Bills chi doesnt even work the same way as everyone else in his own universe, why would it be fair to assume that his soul works in the same way as someone from a totally different story? We cannot say that souls work in the same way in DBZ vs sailor moon just as we cannot assume that relativity affects DBZ and sailor moon in the same way as our own universe.
Bills because he is a true god in the DBZ verse and is universal level and soul steal hasn't been proven to steal the souls of higher lifeforms. Bills has way more years of mental and physical training and conditioning.
Arceus is a god of the pokemon verse and that didn't stop the meteor from owning him or team Rocket from capturing him in the manga. Prove Bills is universal because I watched the movie and he didn't do any universal warping or busting, just flashy ki blasts, punches, and some kicks.