I had also hoped for some golden ending where we could get them to suffer through working together until the brain is defeated, but I really don't think they'd trust each other.
I feel like the closest we could get might be an ending where:
- we successfully convince the Emperor to trust us and take a chance on freeing Orpheus
- we also convince Orpheus that we already have an illithid to get this done and no one else needs to become one
- they work together but Orpheus takes that "the brain is basically defeated, do you betray the illithid companion?" moment and guts the Emperor
- it's vague enough that it's up to the player's interpretation to decide if they believe that the Emperor was actually trying to seize control of the brain at the end, or if Orpheus was just not taking any chances and acted prematurely/instinctively
- player then gets option to kill/spare Orpheus for this, the biggest mess
Ultimately I think one or both of them would still end up dead even if they do work together in that final hour, but it feels better to be able to try and fail than to be denied the chance of trying at all.
I can't imagine siding with Orpheus again though, maybe not until I do a gith run anyway.
"You should have let my honor guard kill you." lol then perish.