Clerics cannot fall though.
If a Cleric works against the will of their deity, yes they lose their faith, but they can simply pick a different faith that supports their actions.
Yes they can.
Clerics get their abilities directly from their deity.
If they go against the will of their deity, they lose their powers full stop. Since their powers are a gift actively granted by the deity.
They can attempt to pray to a new deity, who *MAY* grant them powers, but it's not guaranteed. Nor will it necessarily be the same powers they receive (As each Deity will only provide specific domains to their followers - I.e. Shar will not provide Light or Life domains just as Selune won't provide Death or Trickery domains)
Actually a highlevel Cleric offers a lot for a deity, too, to strengthen the respective faith. So I'm not sure why you would think that a deity wouldnt love to get a new highlevel Cleric for their faith, as long as that Cleric aligns well to the respective faith.
Either way its not the same as a fallen Paladin. Because Clerics dont have to follow a specific code and dont have to maintain a lawful good alignment. They only have to maintain a thinking aligned to their deity and serve their deity and faith in general.
Anyway, all that stuff would be a hell of a lot of work to implement, thus Larian (and for that matter, previously also Bioware) opted out.
In fact, it's a similar notion to what "Evil" actually should be, rather than how it's often depicted in D&D related games where it's all about being a "Chaotic Stupid Jerk".
Yeah I hated this especially in Star Wars: Knights of the Old Republic. You either play a goody two shoes or you kick every puppy you come across.
Would Darth Vader kick every puppy he comes across ? No. He would consider such a thing a waste of time.
