The 4e paladin has various powers intended to support the paladin in soloing in various ways, so that not flanking is not necessarily a mechanical disadvantage.
My preference is that a character be honourable because the character is honourable, not because he is bribed to be honourable by having mechanics that result in his best interests being inevitably served by being honourable. That's not a choice to role play - it's a choice to select whatever approach is most mechanically advantageous.
I also hope I've made it clear that the player in the example I posted didn't think that his PC was doing the right thing by Vecna's lights. He knew he was opposing Vecna, and Vecna's interests, and Vecna's desires. I forced him to choose between the Raven Queen and Vecna - a choice I do not believe he was that surprised to have forced upon him - and he chose. He wasn't surprised that Vecna then punished him by shutting down his imp.
And it has been stated numerous times upthread that a Paladin's player should not be surprised, but should have ample warning that the actions the character is taking carry the risk of losing Paladin status, so there is no difference here between your adjudication and the adjudication of the Paladin's compliance with his alignment restrictions.
The player could, of course, have chosen Vecna. The Raven Queen would then not have had any immediate means of punishing the PC; and at least in the immediate term, the other PCs probably wouldn't have noticed. The player deliberately took the risk of suffering punishment, to which he knew he was exposed - he had deliberately implanted the Eye in the imp to bring Vecna into play as a counterbalancing force against Levistus - because in the play of his PC he had an evaluative response. There are some resemblances here to player wanting his/her paladin to fall.
And the Paladin's player could choose the path of Good and Righteousness, or the path of Expediency. The latter takes the risk of consequences from the Divine Forces which empower him. He deliberately chose to play a character whose abilities depend on a Cosmological Force which has an evaluative response.
They were not taken outside the action resolution mechanics. They were taken as part of the resolution of a skill challenge. Furthermore, it is inherent in a 4e familiar that it may be shut down. And it is inherent in a 4e artefact like the Eye of Vecna that it is somewhat overpowered but also potentially temperamental.
Much as the loss of a Paladin's abilities outside 4e is inherently capable of occurring based on the rules for that class.
You have consistently opposed removal or reduction of the mechanics which enable the Paladin to impact the fiction, but you are OK with removal or reduction of the mechanics which enable the Invoker to impact the fiction. That the removal of the Invoker's ability to impact the fiction seems irrelevant to me - you have been arguing against mechanics which allow the removal or reduction of a character's ability to meaningfully impact the fiction, but you now present for our approval a play example where you apply mechanics which remove or reduce a character's ability to meaningfully impact the fiction.
The key issue for me is that the player's evaluative judgement is not invalidated, nor even called into question, in the episode of play I described.
So it is only the player who says "My character did the right thing" who cannot have his character resources reduced poor removed? That seems very different from your previous arguments. Why does the fact a character doesn't care about doing the right thing make it OK to reduce that character's ability to impact the fiction?
The 4e PHB pp 89-90 characterises paladins thusly:
Paladins are indomitable warriors who’ve pledged their prowess to something greater than themselves. Paladins smite enemies with divine authority, bolster the courage of nearby companions, and radiate as if a beacon of inextinguishable hope. Paladins are transfigured on the field of battle, exemplars of divine ethos in action.
To you is given the responsibility to unflinchingly stand before an enemy’s charge, smiting them with your sword while protecting your allies with your sacrifice. Where others waver and wonder, your motivation is pure and simple, and your devotion is your strength. Where others scheme and steal, you take the high road, refusing to allow the illusions of temptation to dissuade you from your obligations.
Take up your blessed sword and sanctified shield, brave warrior, and charge forward to hallowed glory! . . .
As fervent crusaders in their chosen cause . . .
What strikes me in that is "pledg[ing] . . . to something greater than themselves", the "exampl[e] of divine ethos in action", the "pure and simple" movitvation, the "obligations", and the "fervent crusad[ing]". None of that screams "mercenary" to me. There is no mention of a pact, no mention of a payment, no mention of a readiness to be bought away. And that text, particularly those bits I've called out, expressly contradicts your claim that the 4e paladin is not beholden to anything outside him-/herself.
What strikes me is how poorly those words translate to following an unaligned deity.
Behold, to you is given the responsibility to unflinchingly stand before an enemy of indifference's charge, smiting them with your sword while protecting your allies with your sacrifice. Where others waver and wonder, your motivation is pure and simple, and your devotion to the path of unaligned indifference is your strength. Where others scheme and steal, and fight for the values they hold dear you take the high road, refusing to allow the illusions of right or wrong to dissuade you from your obligations to nothing whatsoever.
Take up your indifferent sword and unaligned shield, brave warrior, and charge forward to hallowed glory! . . .
As fervent crusaders in the chosen lack of a cause . . .
Seriously? A fervent crusader for the cause of unalignedness? Nope, not seeing it!
"If needed, to ensure that characters whose class has behavior restrictions lives up to them or faces the game world consequences."
I'm reminded of the Ravenloft mechanics of fear and horror checks, which were presented as assisting in setting the tone that the PC's are not mindless automatons , beings wholly without fear or dismay. They were presented as saving throws, with the caveat that one need only really invoke these if the players are not role playing fear and horror through their characters.
In similar fashion, if the players are role playing their professed alignments, mechanical alignment simply fades into the background, to be applied only where there is a problem that, really, should not exist. Now, that may well mean it does not add to play where all around the table are skilled role players, but all players are not equal in that skill, and even the best of us can certainly have our off days. For myself, if I'm unsure whether my character would truly be afraid, or horrified, I might well volunteer to let that be adjudicated by the game mechanic and roll the check.
And I might well play my Paladin who truly, fervently believes he is doing the right thing, despite it being against everything he has been taught to believe. And he might well face in-game consequences for those actions, as adjudicated by the person at the table who has assumed the responsibility for assessing the reaction of those Divine Forces who grant my character his powers. And I, as a player, might very well say "I can see the Powers of Good understanding his reasons, and I can see them being unable to overlook his transgression. You, GM, are adjudicating those Powers so it is your call."
Frankly, I don't need the GM's affirmation of my play of my character, or my assessment of whether his actions were consistent with the expectations of some higher power of Good. I played my character's reaction to whatever has caused him to be judged, and I can play his reaction to whatever judgment occurs in game. And if the result is the GM/players congratulating me on engaging role play while adjudicating that the actions of the character result in sanction from his deity, his church, his lord, the Powers of Good or whatever other entity is relevant in game - then it was a great game tonight, and I look forward to playing out the consequences of his actions when we play next.
I don't play to decide how the universe reacts to my character's actions. I can GM if and when I want to decide the reactions of the bit players (like barmaids, townsfolk, kings, high priests, deities and cosmological forces). I play to decide the actions of my character, not the reactions of the world around him.