Warmaster, Warsmith, etc...: depends on how you see it. Of course it's only advancement, you're right in that regard, but it's called Elite Advance for a reason. The principle is that if you reach a certain status, some bonuses come attached with it. So to assuage your doubts:
I suppose it may have to do that we have some different views on what an Elite Advancement is. My view is that if an Archetype is a great road you can walk, the archetypes are about walking in specific parts of the road and its all about specialization within the archetype's sphere.
For example a Berzerker can make you a great close combat fighter while and Warmaster/Chaos Lord will make you great at commanding others. And as I see it once you have picked an Elite Advancement you stick with it as your character gets stronger, and thus I would object to having several Advancements that do more or less the same thing. In regards to having one from each Legion I think its a cool concept but I wouldn't write it out so specific as that kind of makes it impossible for anyone not of that Legion to take it. That can of course and fully legitmate be the very thing you are gunning, but that's my mind on the matter.
If you've got time I would be very happy if you could maybe post the whole list again and perhaps add a line or two about each one of them and what their "thiing" is? For example I could imagine that the Berzerker is to kill people in CC and probably being devouted to Khorne.
-Skull Champion is just that: a more powerful berserker. And why not include it?
-A Talonmaster is a title given amongst Raptors to the most talented of them, and can only be obtained through the murder of its holder.
Why have two Elite Advancements that basically does the same thing?
-Warmaster: warmaster is a very specific title. You could bestow it upon yourself, but without a modicum of power and strategic acumen, you would probably just get laughed at. What the advance says is: alright, you fulfill x and y requirements, you're not a joke, so you get the title, the crown and the perks.
I disagree with this approach, as I think that I've outlined above. If you fullfill X and Y to be a badass you are already a badass and I don't see why you would need an Elite Advancement to get some further perk. I would personally imagine that this is an Elite Advancement for characters wanting to get better at Commanding various things and generally keeping authority over underlings.
-Archeretek: basically just the way of throwing a few technological perks to the scientific-minded adept, and not anyone else. A combat-focused Heretek shouldn't be able to get this one.
What do you mean with an "Adept" in Black Crusade?
-Alpha Psyker: not everyone is an Alpha Psyker. Not everyone knows he is an Alpha Psyker, or is born one. This is a very dangerous, very rewarding advance. Basically, every (very pricy) talent you get makes you more dangerous (for everyone including yourself) and the last one is a shortcut to Daemonhood. Near impossible to get, basically just for fun, as Alpha Psykers are beyond rare and rarely survive long.
Alright. I'm not sure that I'm buying it but I think I'm getting what your after, and its not all bad from the looks of it.
-Champion of the Black Legion: this is kinda specific, as the Black Legion has a very specific mindset in that regard. Plus I'm trying to make one per Legion.
Having a concept drawn from each Legion is a nice and cool thing and if you want to make it Legion specific there's nothing wrong with it, even if I would probably make it less directly tied to a Legion.
-Son of Alpharius/Omegon: very specific mechanic. Kinda fun.
Mind telling me/us?
-Warsmith: specific enough to warrant an advance.
I suppose its about allowing Chaos Space Marines to get hold of tech-stuff, right?
-Chaos Lord: for the battle-minded Traitor Marine. But you better have the 50+ Legionnaires under your command to back it up, or you're laughing stock.
Ok. I'm not sure since your saying that its battle-oriented but that you need 50+ Chaos Space Marines and that kind of hints that it might be a socially/intellectually inclined Advancements. At least to me.
-Plague Lord/Marine: same thing as Skull Champion/Berserker.
I can see the desire to play a Plague Marine so that's cool.
-Exalted Champion: if you're your run of the mill combat-minded Legionnaire, it doesn't get much better than this.
Ok. So its just more combat stuff for a Chaos Space Marine, who is already a combat monster?
-Night Haunter: I know, it was just a stand-in until I get an idea. I might replace some advance with rules for the creation of Traitor Legionnaires with advantages/drawbacks.
Alright. I assume that this one is inspired by the Night Lords and probably works around psycological warfare, intimidation and stuff like that.