I think the Council of Trent is a nice idea overall, but the current implementation makes it one of my least favourite features.
1) It seems way too random.
Like in the example of the original post, most cardinals wanted Conciliatory, as did the Curia controller. Yet Harsh was selected for some reason.
I did a test in game once, reloading a save from before the council. Original result was All out Harsh. New Result was All out Conciliatory. No major changes in political environment either, but it is ofc possible that I missed a Curia controller change for example.
2) It has too big an impact
There's a -120 opinion difference between max Harsh (-80) and Max Conciliatory (+40), which is insane, considering you only get -100 for being someone's rival.
With Conciliatory, inter-faith diplomacy is easy mode. With Harsh, alliances break to one bad event and PUs can be tricky to keep, let alone integrate if you're a Protestant with Catholic subjects, since you get -120 total from different faiths if adjacent, -100 if not.
3) The opinion modifiers last too long.
The modifier really should end when the faith of the HRE is decided, instead of lasting till the end of the game.
In my opinion it could use at least some of the following changes:
1) Having it depend more on the number of Cardinals for each stance, and the Curia controller. There could be a longer cooldown between the choices, so it would be more likely to have more than one Pope selecting options.
2) Reducing the opinion modifier by 50% would make sense
3) The opinion modifiers should have an end date. For example when the HRE faith is locked, or just a fixed year like 1650 for example