Ok, so I think I'm getting a sense for things, let me know if I'm right. You like settings that by their nature provide an overarching quest. Like if you're in Ravenloft, by definition you're trying to get out. Likewise, if you're a mage in Grati, by definition you're trying to become one of the elder magi. Of course, the problem with these situations is once you succeed, your adventuring really does come to an end. If a dark lord escapes Ravenloft, his domain collapses. If you become an elder magi, you're now on top of the world.
If you want to do this with Waterdeep, it could be difficult as I had no specific end-point in mind, as you know. I was thinking less like a novel and more like a comic strip, which is to say episodic. I do want to get into some epic levels with this campaign, but it doesn't need to be far. The campaign could have an overarching quest and then end in epic levels, with following campaigns happening in the world after the first campaign. If we don't come up with an overarching plotline, we can just suggest that players retire their characters when their interior plotlines have reached a resolution, idk.
Some more stuff you should know. The illithids I think are basically going to come from a future Greyhawk setting. They come from the original Greyhawk setting. Part of the Greyhawk setting is actually this problem of magic weakening and draining away. Some philosophize that the more mages use magic, the more it's used-up, so to speak. Boccob, who as I recall can time travel, never finds the solution to this problem. I was going to have it be a result of the fundamental supernatural laws Greyhawk was built on when Jeriah Chronos initiated its timeline. It might have something to do with Greyhawk not having a weave which holds magic together. In any event, magic disappears in Greyhawk's future, and this allows for the rise of technology. Eventually, psionics also develops, as there is still supernatural power concentrated in the individual soul even if Greyhawk doesn't have a weave. This results in at least one serious change with my game from published material - my illithids are not at all sorcerous. They are all psions or martial types. I always thought it ruined the flavor to not have them be psions anyways. In any event, one additional major reason for why they're so threatening is because they reached their power level only on psionics. Now they've gone to the past and to other worlds entirely where magic still/always functions. If they had mastery over psionics and the various forms of magic, they would be incredibly powerful. There is a league of individuals trying to oppose the illithids, largely composed of spellweavers, and needless to say one of their main objectives so far has been to keep the illithids far away from learning any magic. Up to this point, they've been mostly successful. But the occasional multiclassed illithid wizard can be found.
The illithids traveling back in time was how psionics and advanced and modern technology were introduced into our timeline. Gnomes claim to have invented some advanced technology of their own, but for the most part they've just been lying to people with their superior illusion magic, lol. To their credit, though, the gnomes have been the best reverse engineers for mass producing advanced technology. The illithids would have rather kept this unique power sources to themselves, but necessity has forced them to trade with the drow and others, so a fair bit has disbursed to the general population. Mind, technology is still rare enough that it's expensive (as it should be, because it's generally more powerful) and that it doesn't change the essential high fantasy setting. So it's like high fantasy infused with Final Fantasy.
Concerning the name Jeriah, I agree it doesn't have the greatest sound. That's simply his parent-given name recorded in the history books. It means "taught by God" which I thought was rather appropriate. We could say for that reason, and because it is a humble name, that he always hated that name and took simply to calling himself Chronos. In most ancient cultures, individuals only had first names. At most you would have a first name and then "of [your city]." Like "Josh of Vancouver." So Jeriah may have been named Jeriah Chronos by his Netherese colleagues to distinguish him from other Jeriahs. But he may have preferred another name entirely, or later he may take on another name entirely for the sake of anonymity. Anyways, open to input there.
What I was hoping to achieve with the map is to have all the layers fused into one jpeg except the sewer tunnels and stories 2 and up. Obviously, from a bird's eye view, we can only see one level at a time, so I want that to be the ground level to start with. I would still like to see all the sewer access points if possible, but if that involves tediously separating them from the sewer PDF layer, then don't worry about it. I would like to have all the other label layers though. Obviously these will be painted away before players can see them, but while we're still building the map it would be nice to have them around so we know what areas need to be populated with artwork and what kind of artwork we should be using.
So, with what I've said above, I was intending on granting access to all officially published campaign settings and mechanics, including d20 Modern, d20 Future, and Pathfinder, in all mediums - books, magazines, and web. The easiest stuff to access is stuff from the core books and the Forgotten Realms campaign setting. OP things and things from other settings are harder to find, but they're still not considered homebrew.
So how I was thinking of handling homebrew is, you decide at character creation whether you'll use homebrew material or not (either way we'll have to give it the clear, of course). If you don't use homebrew, you gain another benefit instead. I was thinking that would be special knowledge. Maybe one item of special knowledge per level - that might be too much though, IDK yet. What I mean by special knowledge is a way to bypass knowledge checks to get access to OP stuff. In other words, normally you would need a high knowledge check to know the Wizard's College is experimenting on students. But if the DM writes into your story that one day you noticed said experiments while walking along, then you have the knowledge in spite of a check. So we might put players in libraries and have them luckily read exactly the right book for their characters or whatever. Then they know how to become a circle mage or something.
You're allowed to populate some of these other worlds if you want, but I was going to focus on the main timeline in Faerun and leave the other players to homebrew worlds if they liked.
So I suppose part of what's needed at this point is the decision to go or not ahead with these premade campaigns. That would require me to read them though, lol. I'm so cramped for time ATM. I might be able to read them in a couple weeks, but no sooner. They obviously won't already have an overarching quest, so we'll still need to figure that out. But it's hard to figure that out without know what they are about.