The whole idea of "no take backsies" screams player entitlement to me. Why shouldn't a god have the ability to remove that little spark of the divine he gave you, if you're constantly and seriously throwing it in his face?
Because it's more interesting that way? By your logic, the gods should basically be engaging in mass mayhem, but generally in D&D settings, they aren't, because it's more interesting that way.
If the god can take it back, the whole thing is a trivial matter, akin to revoking the access rights of junior employee at an IT company. There's limited RP potential, especially if, as you've suggested, you only lose 1/3rd of your powers, and can get them back simply by getting re-hired by another IT company.
Also "entitled" is hysterical. Yeah, being hunted down by teleporting zealots with two-handed swords is definitely something "entitled" people seek out. How is it not more entitled to expect to just be able to regain your powers by apologizing, doing a ritual or getting re-hired? That seems obviously more "entitled", to me.
And an intelligent player can easily hide his misdeeds from the public view or scrunity (who will tell on him from the depths of the dungeon? Probably not his teammates, who aren't under any oath). But nothing escapes the eye on the sparrow, neither deed nor even base thought or desire.
You're assuming all D&D gods are completely omniscient, then? That goes rather against most D&D settings. If they are though, again, this is pretty interesting, because assuming they're omniscient not omnipotent (because no D&D setting has ever had omnipotent gods or even particularly potent ones), they presumably communicate the PC's sins (or NPC! This makes for GREAT badguys, you know!) to some senior figure in the church, who puts you on his list and sends people out to get you.
I hope this becomes an optional rule, because I don't think it's up to a god's followers who conveniently are never around to bear witness to his misdeeds, to discipline his champions.
What are you talking about? Seriously, did you read my post you're quoting? I'm suggesting this as
one way things can work. I seriously doubt that it will be the default, and am not suggesting it should be, but you apparently believe I am. Care to explain how you came by that belief?
I'm fine with it being an optional rule to enable this, but I do not for one second buy the gameplay or fiction reason why there shouldn't be a severe punishment for Oath violation. Oaths aren't pillow talk. They are serious business, from serious powers (what's more serious than a God in D&D? The DM only, and those are effectively the same thing anyway).
I find it truly strange that you think having an entire religious organisation full of people with similar powers to the PC or NPC angry with them is "less severe" than, as you've suggested, temporarily losing access to 1/3rd of your class features. To me the former seems vastly more severe, and to have a vastly greater amount of both RP potential, and campaign potential. It seems to me that it's a lot easier, under the methodolgy you suggest, to just ditch your god and pick a new one, merely experiencing a period of undefined length where you are inconvenienced, than having to convince a whole bunch of zealots that, no, really, you have repented!
To be clear, I'm not suggesting it "should be" the 4E-style way - you don't even really need optional rules to make it the 4-style way, either, just a lack of them. But I do think it's actually the way that has far more campaign-impact, RP potential, and real threat to the PC than what you're suggesting. Which is not to say that your suggestion has no value - it's actually quite workable, and works well for campaigns where you want the possibility of falling, but you don't want severe consequences, or campaign-altering consequences, just a period of the PC being weaker.