Why don't we see if I can get through the rest?
JEFLIV's Versatile and Shielded: While I understand the desire to make a Pokemon that fits a certain mold, doing something like this is not really what the CAP project is about. We are looking more for something that can guide the community in making something that teaches us about the game than something that is simply the guide to making a specific Pokemon. I suggest you look back at the rules in the OP to get a better idea of what I mean.
Lster728's The Mixed Marauder: Well, first off, having specifications of stat bias in the general description is something we generally want to avoid, since it dictates too much of the process before the discussions even begin. That being said, I do think the idea of what makes mixed sweepers work may be worth exploring. One of the phenomenon in Pokemon that I find most interesting is that some Pokemon with good mixed attacking stats (such as Lucario or gen 4 CAP 1 Syclant) are only usually found attacking from a single side of the spectrum, and in these specific cases, the side with their lower offensive stat. Investigating what truly makes both sides viable and how to achieve this without making one side clearly superior could be very interesting. I would however suggest that you focus you questions a bit more. While they do address some important matters, I think you need to also get more into what exactly we can learn from it.
WhiteDMist's Pascifistic Stall: Honestly, I can't remember seeing a concept like this before, and that really surprises me, since there is a lot of good stuff going on here. While stall is often brought up, the specifics of PP stalling are not something we have ever taken the time to look at in depth. I like this concept because it is at the same time very focused in goals, but very wide open in how we can execute it. While the lack of a Pokemon like what we may make in OU may mean that the specific PP stall info we gain might not be the most transferable, I think this concept has the potential to teach us some about win conditions and the difference between heavy dedication and versatility that would be useful throughout the game of competitive Pokemon.
CabooseFTW's Arghonaut 2.0: Of all the ways people have gone about trying to "fix" the meta, I think this is one of the more interesting. The fact is, the playstyles that exist are far to large for a single Pokemon to take on, but looking simply at 5 individual Pokemon and how to stop them is a much more viable concept. The original Arghonaut was designed with decentralizing the metagame in mind, but after having done the project, we discovered that it didn't decentralize it, but simply recentralized it. Pokemon is always bound to be a centralized game, but it is certainly possible to mix up what it is centralized around. I will say that I think you need a bit more focus in the concept though. Right now it seems mostly about simply changing things for the sake of changing them, and I'd like to see a bit more on what exactly we can learn from doing it.
DetroitLolcat's Lets (Not) Get Physical!: Let me start off by saying that this concept immediately caught my eye with its mention of "thoroughly explore the Physical/Special split of Pokemon that occurred in Gen IV." While this is something everyone takes into account every time they play the game, I don't think anyone has ever really taken an in depth look at it. That being said, I feel the concept is both at the same time too free and too restricting. On the one hand, as long as we can wall the physical threats, the rest doesn't matter. While I don't mind freedom, I do like focus, and the lack thereof can turn certain stages into more of a "what's cool" discussion, rather than one about anything worth learning. At the same time though, countering all the top physical threats is something so restrictive, I am not sure it is even possible. As you said, those things that used to be able to do it simply can't any more, and I have a hard time believing that if they can't that anything can. I mean, sure, we could just make Skarmory v2 with base 120 HP, but I don't see us learning that much from it.
Birkal's Cripple Drizzle: Oh man.... this one is going to take a bit more of a response than most. Hmm... how to begin? Well, let me start off in a general sense about weather. Obviously, this is not the first weather concept to come up. Many have been presented already, and much of my responses to them have been about scope, viability, and the value of the info from the result. The ones that I have responded the most positively to have been the ones with more limited scopes, ones that seem possible to pull off, and ones that would give us valuable data that is transferable to OU. On the other hand, the ones to which I suggested major changes be made have generally been ones that I feel try and do too much, attempt things no one reasonable Pokemon (or just no one Pokemon, period) could hope to do, or simply try and change things about weather solely for the sake of changing them. With all that said, I feel that this concept has crippling fundamental flaws that make it fall more towards the latter group of concepts than the former. Now, let's be frank: what you said about Drizzle being the top question of the day is no doubt true. However, I can't see how the Create-A-Pokemon project can really help address this issue in such a direct manner and still hope to get valuable information out of it.
As I have been saying to nearly every person here, I think the key is in the questions, and so that is where I am going to go into the most detail. As I already said, I think the concept has major fundamental flaws, and one of the biggest is made incredibly clear from the first question. "What is the BW2 metagame like without Drizzle?" Many concepts have already suggested trying to "counter" weather, and to all of them I responded by saying they were not feasible. This right here is the mother of them all. This concept is not simply asking to counter rain (which is already a near impossible task for a single Pokemon), but the learning goals it sets in place are dependent, not only on countering Drizzle, but making it a non-factor in the metagame. Honestly, I would consider the very notion of this being possible to be ludicrous. Subtraction by addition simply doesn't work in that sense.
The other question that highly concerns me is the last one. Suppose for a minute that this was possible to do; that we created a Pokemon that not only countered rain, but flat out took it from the metagame. Is that Pokemon broken? Well, even assuming that it was somehow made so that it was not a major threat to non-drizzle teams, and in a non-drizzle meta would not be considered broken, what will our actual assessment be? Well, if you want drizzle gone, then either it is perfectly fine or it being broken clearly means drizzle is broken. If you don't, then the project will either simply have failed at some point along the way, or our Pokemon will be broken and we are clearly all fools for thinking that you can counter any playstyle with a single Pokemon. In any situation, even in a such a perfect one as this, the success or failure of the project comes down mostly to confirmation bias.
Basically, to summarize my thoughts on this concept, it tries to do too much, while lacking the potential for much benefit. I highly doubt that this concept is even possible to do, I don't think that doing it would help convince people one way or the other, and the lack of realism in the metagame it would create would make the little info we could gain from it hardly transferable back to OU. While I have been trying to make suggestions to each person on how to improve the concept, most of these have been general ways to make a good concept (tailored to the specifics) that I know you already know how to do. The problems I have here run very deep, and it would likely take a significant overhaul to make this something that I would consider worth pursuing. If I am to suggest one specific thing though, it would be to try and make the concept more realistic to complete. As I said, subtraction by addition simply won't work, and as such, any Drizzle, or weather in general, concept needs to focus more on what we can learn from reducing "problems" and not about trying to eliminate anything completely.
Lol cakes's Sweeper Spook: The biggest problem I have here is that I find it hard to believe the move is going to ever be worth using if it is not currently. Look at the Pokemon who learn Psych Up. It is a massive list. Yet, not a single Pokemon there uses the move frequently. Why? Well, you could Psych Up to gain that Salamence's Moxie Atk boost, but then what is it doing? Hitting you with Outrage. Well, what about on set up? If you are slower than Volcarona, you could Psych Up after it boosts to stay on level with it? But in that case it is just an inferior Snatch. Now, don't get me wrong, I'm sure there could be a gimmicky use for it somewhere, but I don't seeing that being a great focus for a concept. If you want this concept to go somewhere, I would suggest looking more into the explanation part, specifically with a couple of sample ways in which this could actually be viable, because right now, I can't see it.
Meganium Sulfate's Labyrinth Wall: Well, this is another wall based concept, similar to ganj4lf's, but with a slightly different spin. Rather than a lack of support, this has a lack of offense. This could definitely be interesting, but I'd like to have more of a goal in mind. I would suggest adding more, especially to the questions, on what we will be looking to learn from this. As I said at the start of the thread, concepts that are simply "let's do it and see what we learn" are not the kind I am really looking for.
SlimMan's Substitute Abuse: I remember either last CAP or the one before someone submitted a substitute related concept that I really liked. While the approach here is different (the old one was about beating sub users), I think this has a lot of the same upsides. In my mind, Substitute is one of, if not the single, most important move in competitive Pokemon. It has so many different effect and so many different ways to use it, but at the same time is not a wholly positive move. While a lot of concepts have been focusing on the issues of the day, this here focuses on the issue of every single day. There is a ton to learn about this move, and this is a very well formulated concept that could help teach us a lot.
Paradox's Scout: As you say, Kitsunoh was a scout, but the scouting game has changed so drastically since Kit was made that what is necessary to be one is very different. This is honestly a very different approach to things that I have never really thought about and I do think it could be worth pursuing. Last gen, a lot of what scouting was involved figuring out the opponents team. This gen, that is no longer an issue. Team preview means that you know exactly what you are facing going in. This leaves scouting in a very different position of being about finding out movesets and EVs and the like. It is definitely an infrequently looked at concept that would be fun to explore. That being said, I would like to see some more detail as far as specific goals. Your questions are a good start, but I think you can get a bit more specific as to what we want to learn about from it.
Well, that should bring me up to present. I'll be looking back over and commenting on changes people have made later in the day.