I know a character can choose to lower their resistance to allow a spell to effect them, but that got me wondering if a caster could choose to not inflict the full effect of a spell that requires multiple saves.
For instance, balefulpolymorph. Could you choose to allow them to keep their mental faculties or do they have to roll and let the dice fall where they may?
They would still have to role. If you want to turn someone into an animal but keep their mind use Beast Shape. Beast Shape 2 will allow you to turn into animals from tiny to large size category.
Cool thanks. For an evil organization I want them to have all of their henchmen as animals using SU and spell like abilities.
Or since you're the GM, you could just have your evil organization create a variant of the spell that drops the second effect. You can even have the players find a scroll of it, as explanation.
Depends on the status you want to inflict.
For example, I can choose to not give you a bloody nose when I punch you in the face, but I can't choose to not bruise your skull.
If the status is an inherent part of performing the action, you can't choose not to inflict it. If the status is something that's a completely separate entity from the action being performed, then yes, it can be chosen to not inflict it.
The catch in researching an alternative spell that leaves out one of the effects is that in all likelihood such a spell or class feature would be a lower level than the original because it has less effects.
A better solution, IMO, would be to house rule the spell to say what Weirdo suggested - simply make the text state "when you hit a target with this effect, you may choose to inflict..."