Since my avowed goal is to now reassemble all of the elements of the Adventure Path into a campaign arc that's more to my liking and much less like a kitschy D&D railroad, now that I've done that, I should go through my summaries of each adventure and in turn turn that into a single summary of the entire AP.
Rather that look at specific elements (i.e., encounters and stat-lines) let's look at concepts and see what looks usable to me.
- being shipwrecked on what is basically Skull Island
- a city of high civilizational colonists in the savage tropics
- caravans and/or river trips through the jungle to more far-flung, and more native-style cities in the interior
- if cannibals and headhunters aren't sufficiently intimidating, the module makes them become 1) undead, 2) lizard-men, 3) snake-men, 4) frog-men, and 5) intelligent apes and monkeys.
- There are both reptilian (specifically serpent) and ape related demonic cults. Not all of the cultists need to be lizard-men, snake-men or apes themselves.
- two separate partitioned cities which are at war internally via local tribal politics. One is underground, but that can be changed if desired.
- a race to discover a lost city against several factions
- a contest to take control of the city against those same factions
Although the idea of a city broken up into multiple factions is a little weird; it's more likely that that's so unstable that one will have wiped out the other ages ago, or at least chased them into another territory, I admit that this part of the adventure path is quite intriguing. I'll want to find a way to implement this somehow; although I admit that I think its all a little too exotic too. Why do we need to have apes and snakes and frogs and daemon-people, and plant-people and morlocks, etc. all jockeying for position. Are there any just plain people-people? (The answer is technically yes, but they're surprisingly insignificant.) Although I tend to not complain about the "Star Wars cantina scene" vibe in D&D, I do think that in this case it's been overdone to the point of caricature.
At a higher level, once we get to the location where the rest of the adventure path takes place (the ruined city and the other ruined city beneath it), I think we can really explore the concepts of the adventure path; who are the villains and what do they want?
Honestly, that's how I prefer to build campaigns; take two or three villains with goals, and just describe them, and let them collide with the PCs. Eventually, each PC might develop their own villain/nemesis or whatever too unrelated to the campaign ones that belong to the group as a whole, but that's mostly to give variety over what is, in effect, a television show's season worth of material. Although only so much can be done about that until I have PCs, so...
In that sense, who are the players and how might the PCs either ally or oppose them?
- advanced people establishing colonies and/or bringing civilization to the boonies. The PCs might well be sympathetic to these guys, but there are more than one faction looking to be the first to claim the resources here, so not necessarily. Just as in the real Scramble for Africa, it's not like France, Germany and Great Britain all saw themselves as interchangeable; they wanted to beat their rivals.
- natives of various types. They are often secretive and hostile, and they resent anyone else intruding on their turf—or they seek to exploit the colonists against their native rivals before stabbing their erstwhile allies in the back. I'm not a fan of the native sympathetic colonial bad narrative that seems to have taken over every single story of this type ever told, so I'd almost certainly eschew it if for no other reason than because it's tired and cliche by now. While some individual natives might be friendly, their societies are strange, alien, and generally not sympathetic.
- King Kong esque gorilla demon cult, and the king of the apes (that actually wants to replace King Kong, not serve him.) Includes a marching army of apes and baboons.
- Lizard god (Bokrug?) that his scaly servants (snake-men and lizard-men) want to bring bodily into the world to conquer the mammal races.
- Other daemon cultists, or even daemonic humanoids (the urdefahn, in the AP) who are attempting to establish a beachhead here.
I don't like the idea of these cities being "ruins" that are yet inhabited by non-human savages; why can't they just be actual cities that are off the beaten path, maybe lost (or maybe not) and the various powers are trying to establish key trade routes, rather than find it and claim it per se?
I find that the snake-men and ape agendas are a little too local to work for me unless they're allied with someone. As in the French & Indian War, I think my French and Indians need to be allies; i.e., one of the factions from the first bullet point above is allied with each of the factions below it (except for the second bullet point, which is just hostile noise, for the most part.
I don't like the idea either of the PCs shipwrecked and finding ancient maps; rather, I like the idea that they're already agents (or will be from very early on) for one of the factions. The shipwreck and the jungle cruise can be combined into a single jungle overland jaunt, with some politics and whatnot when they arrive at their destination. Although instead of being in a single city, I think the various factions need to be more separated. The PCs wandering inadvertently into a war, with some one-off bad guys here and there (vampire predators, Lovecraftian monsters, etc.) maybe more maybe not borrowed from the module, works better.