Heh... perhaps I was being a little snarky. I'll rephrase.
Yeah, you kinda were... for no reason.
What is the tangible benefit of maintaining a direct correspondence between a metagame class term and its name within the game narrative?
Well for most people it easily serves as shorthand for an overarching and high level character concept... I wanna play a holy warrior in shining armor... paladin. I want to play a hunter or tracker... Ranger. A wielder of arcane spells and knowledge... Wizard. A stealthy thief and ne'er do well... rogue. And so on.
I guess my question to you is why have these names even been used and why do they have specific fiction attached to them in the game books if all they are suppose to be are packages of abilities? It seems if they are to be flavor neutral... you wouldn't attach specific narratives to the classes. As an example the narrative for a warlock is different from that of a wizard... so why do this if really all a warlock is suppose to be is a "striker" wizard? Why include the narrative of him having made a pact with some entity instead of learning from spellbooks... why include specifc beings that he can make pacts with... and so on if he's just a package of arcane striker abilities? Recent editions (at least from BECMI onward)the books have never supported the classes being just a grouping of abilities with no attached narrative or fiction.
Can a DM rename paladins "Chevaliers du Orlais" in their homebrew?
I don't see why not... though I would still tell PC's that this is an order of paladins since that in and of itself sets up on a high level what this oprder is about. Or would you just present this name and not explain what type of class they are composed of?
If so, can they use Avengers to represent (some or all) of them?
If it's all of them...then I would argue that they are an order of avengers and it's actually misleading to claim they are paladins... isn't it?
Stealthy, lightly armored, holy assasins are the picture that the narrative in the book and the class abilities of the avenger paint. I know if you told me they were an order of paladins or even holy warriors as opposed to holy assasins...I think I would be expecting one thing (expectations I would argue are backed up by the fiction in the gamebooks as well as the mechanics) and would be irritated when I finally realized that none of that applied and I should have instead been reading the avenger entry as opposed to the paladin or even cleric entry.
A mixed order, on the other hand... I would read over both and pick the archetype that most closely fit my concept, either holy warrior or holy assasin.
Of course the problem here is what we have been discussing... I'm not just picking the archetype that matches my concept best... I also have to deal with combat role being specifically attached to the archetype. So I can't enjoy the gameplay of a striker but want to play the heavily armored holy knight that strides forth and cuts down his enemies. Instead in picking that archetype I've also made the choice that my gameplay in combat will be defending, not striking.
What about swashbucklers? Should they be fighters? Rogues? Their own distinct class?
In 3.5 there was a swashbuckler class...
How much does nomenclature matter? Why does it matter?
I would say it matters as much as the game makes it matter... and the fact that specific narratives and fiction are attached to classes in D&D... has made it pretty important. Now if there was just a name and a listing of abilities I could somewhat understand your argument (and I have games that do this), but D&D has never been like that, there has always been story and narrative as well as defining mechanics attached to class. You can change that if you want, but then you are going against the baseline expectations of the game set in the PHB. Nothing wrong with that at all if that's your thing but I think you then need to inform your players on what the chnage is to the fiction and narrative (and class mechanics if you change that as well) otherwise they come to the table with the expectations that have been set by the books.
Feel free to answer any of this. But if you're going to respond with snark or wit, at least try to funny.
Don't see the point of snark.