I wonder if they could just change the first time the tadpole is introduced to the helm fight. If using the tadpole was the only way to get the cambion sword, I think that powerful weapon is more of an incentive than adding SH on the ship or a few minutes later on the beach.
They could also lock the gith relic behind a tadpole locked container aboard the ship. It would allow the PC a chance to get the relic without having to murder SH. I think it would be a suitable temptation.
