DoN:
Admittedly I do find it a bit of a struggle to creatively contribute, as the lines are a bit blurry as to what can be changed and what can't and so forth,and how much of an 8.ed upgrade we're really going for.
I imagine the original skeletons were also voted on originally, and so were the cultists etc. I don't really have a real grasp of what were "popular" when the army was first being created for 7.ed either. It is not so easy as far as many of the units go, as they tend to have little fluff compared to let's say the characters in the list, so it is a little hard to judge what one can suggest without stepping on any toes. To me, a well defined unit typically has good fluff backing it, and when the fluff becomes vague and general in its description it also becomes hard to judge how strongly people originally felt about it. If it looks like it was thrown together with little or no fluff, with a handful of people not participating any longer voting on it, it is very difficult to judge for someone like me today what really sold the unit to people back then and so on.
I'll hence forward ask if I can be allowed to offer a suggestion for a unit alteration, and if you judge the current unit "unchangable", I'll just save it for my own little LoN project that I can perhaps one day finish (after the Legacies project that is).
I know that part of the reason why I disagree on things here and there, is because I tend to take a less "epic" approach (4.th ed Undead book angle) and lean a bit more towards having the option to actually depending on playing more tactically instead of having a more expensive/more dangerous character or unit to win the game for me in a classic toe-to-toe approach.
I like that challenge to play well to win to be there, so I'm perhaps leaning more towards a better army synergy (with weaker units forced to work more together), instead of ultra-powerful units taking on enemies by themselves. I do however understand that most
VC players (hence members on this forum) tend to be naturally attracted more to "powerful characters" or just "power" in general than the average warhammer player player (that is my overall impression at least), and that I might be facing an uphill battle here. The "host" of 4 wounds Vampire Lords with all kinds of "kill-me-not redundancies" fount in the Necrarc's Workshop section sort of gives one a broader glimpse of the psychology of the "average" Vampire counts player.. hehe
Also, I like the Nagash triology by and large, and since this list was created before their time, I think we're robbing ourselves of the by far largest volume of official information on which to base the army fluff etc. I am quite partial to including more from these books, to take it a step along towards the present "official" take on things. I realize however, that this is next to impossible if one is to stay true to the voting that took place before these releases.
I just think it is worth the extra effort to create something that is not so "4.ed", if at all possible, and I would be open to contribute quite a lot to compensate for "lost" work to see this come true; but I also understand that you feel that you have to stay true to the vision of the original contributors/voters and are thus restrained from going that route.
As to your question, it somewhat clears things up. It is the "existing units and fluff being dropped for
"little justification" part that leaves things a little open to personal interpretation.

In the end, you are the judge of what this really entails, and anyone wishing to contribute basically has to convince you that it can/should be justified (since most of the original voters seems to contribute only very sporadically at best)...
On to the specific points:
-Locust: I think this should really be separated from access to the rituals at the very least... That would leave us with more heroes allowing units to march, without many Locusts themselves becoming overly powerful, assuming the idea of rituals stay as they are currently.
-Black Armour: A Heavy armour (5+) with Immunity to Killing Blow is certainly not unbalancing game-wise, and also unique as far as an army-wide armour goes, which I think is a good thing. It is also a good
TK counter in the sense that it protects us from the "Djaf's Incantaion of Cursed Blades", which is pretty fitting considering Nagash's hatred of them etc.. Not an expensive option on units either, which I like.
Immune to Poison is a bit strange on an armour protecting someone that should rightfully not be subject to poison in the first place, so is having armour with little or no openings where one can strike the wearer within to deliver said poison. This said however, I think we should stick to one of the options if this is chosen, and I'm leaning towards Immune to Killing Blow of these two options. We have to be careful of not making too many redundancies in the list overall, as that sends a bit of a "nothing is supposed to beat this unit" kind of a signal to other players interested in playing vs. the list.