Voluntarily failing saving throws

[Betelgeuse]

so i decided to play around with the contingency spell and reuse a tactic from baldur's gate 1 - when a character gets near death i cast otiluke's resilient sphere on them. if the monster wants to continue attacking that character i know it'll stay safe.
that plan seems to have gone out the window now. cast the sphere on a character, make a save vs spells and waste the spell. i don't suppose there is a way around this? to make the character fail the save on purpose, seeing as its a beneficial spell. like how it is written in 3e - 'will negates (harmless). This spell is usually beneficial, not harmful, but a targeted creature can attempt a saving throw if it wishes.'

[Dragonshadow]

Aside from hacking down their saving throw in shadowkeeper or somesuch or casting a saving throw lowering spell (I don't know if one exists though), I don't think you can.

[CerebroDragon]

Obviously since your characters should logically be of a higher level in BG2, their saves will reflect that fact and be all the more better, thus making the tactic more difficult to pull off.

If you're really desperate to get it working, I guess you could always try lower resistance spells or greater malison and such, but it does seem to be based on an odd and slender premise. Good luck with your experiments in any event.

Shame you can't target Sanctuary spells on heavily wounded tanks or have a higher level version of it that works like Otilukes Resilient Sphere. Or maybe there is one that someone has made or I'm just forgetting something.

[Illumina Drathiran'ar]

Get Aerie to put three Dooms in a spell sequencer.