In light of my dredging up the wreck of the abortive FALLEN SONS project and trying to make it seaworthy, I've got some very early baseline thoughts to focus on. The first major question I need to address is which of two high level models that I want to use. For lack of a better term, I'm calling them the Thundarr model and the Warhammer model. These aren't meant to be exact, more like elevator pitch type comparisons.
The Thundarr model is a post apocalyptic world of super science and magic. If you're not familiar with the early 80s post-apoc sword & sorcery cartoon Thundarr the Barbarian, you should be. Because it was the early 80s, the animation is somewhat cheap, the stories are somewhat cheesy, and the violence is toned down to an almost insulting level. But once you can get past the idea that that was an element of 80s cartoons that you simply aren't going to be able to get away from and can look past it, then Thundarr the Barbarian has a lot to offer. In old school sword & sorcery style, the villains are the sorcerers, and by sorcerers, I usually mean a weird combination of transhuman super science and bizarre magic. Sorcerers can be more or less stereotypical dark lord types, or they can be brains in a jar with robotic arms that shoot lasers. The setting is clearly post apocalyptic America, because it makes a point of always showing broken and derelict recognizable places, like Ellis Island, Las Vegas, NASA headquarters and more. There is no functioning society; small tribal villages of poor Americans who are downtrodden and oppressed by either the armies of the sorcerers, or other monstrous incursions that have taken over in the wake of the apocalypse are the damsels in distress. Thundarr himself is a kind of stock pseudo-Conan barbarian with a lightsaber, and his sidekicks are a vaguely lion-like Chewbacca analog, and a sassy sorceress who turned her back on her evil "father" and followed Thundarr because he's a good dude and pretty sexy, and she'd rather be on his side than that of evil. She's kind of like a less demanding and entitled Princess Aura, who is deliberately made to be much more likable and sympathetic.
I like the Thundarr model because it's somewhat fresh and different (despite it's age and vintage generally) and few properties have been like it over the years. That said, fresh and different is often indistinguishable from weird and different, i.e., people won't like it, including once the novelty wears off, even me. Of course, when I say the Thundarr model, I don't mean that too literally, but rather that I'm positing a post apocalyptic grimdark(ish) setting that feels like the apocalypse happened in a world much like ours. People will often look weird and Mad Max-like, and the remnants of higher technology will play a key role in the setting here and there.
On the other hand, I don't like the Thundarr model because I also fear that in having to focus on the post apocalyptic stuff, that I may end up diluting to some extent the high concept of a world over-run by daemons. It's kind of its own high concept that's similar—at least in some respects—but different in others. Even as the developer (me) I'll get often distracted by things that are not related in the least to the high concept of FALLEN SONS as its initially defined. Of course, as initially defined, if you want to be technical, includes this option, as it was initially defined as a world pretty much exactly like ours.
The Warhammer concept isn't meant to imply that it's too similar to the Warhammer setting (either the original or the bizarre Age of Sigmar reboot, merely that it would be a vaguely similar grimdark(ish) standard European Medievalist fantasy world overrun by daemons. I doubt that I'd have anything even as friendly and cozy (not that this really qualifies for those adjectives) as the Empire; rather, the Empire would be a distant memory as a polity that failed under the daemonic incursion. The "points of light" flavor would be seriously ramped up, to where the points of light are tiny islands under siege, in a sense, against the darkness without. Daemonic kingdoms or demesnes, or whatever you will want to call them aren't necessarily overtly and simplistically hostile, although they are insidiously hostile at all times. Much as Azzagrat/Zelatar, or various places in Hell or the City of Brass were—well, friendly is the wrong word, but at least possible for regular people to wander around trading, using and having activity in—these daemonic kingdoms can be visited, although various dangers are always lurking under the surface.
I like this because it's familiar and in fact even classic without feeling retreaded or cookie cutter vanilla. The high concept makes it different from most fantasy, including the default D&D or LotR or Conan the Barbarian models. It's neither extruded fantasy product nor thud and blunder, so to speak, because it has at least some bit of a twist on them. It's easy to pick up and play without having to overthink much about the setting, which puts the focus squarely on the high concept, because everything else fades into the background.
On the other hand, I don't like it, because it just feels like it's going to be very similar to what DH5 already is, except with more daemons. I already kind of have a dark fantasy vibe to my fantasy settings in general. Is it sufficiently different from what I'm already doing that it's worth spending the time making what amounts to small tweaks and whatnot to my existing projects? Or, on the other hand, is there something about it that I can make really stand out to make it truly feel different?
That's the major decision that I'm noodling first and foremost, and the answer to it determines some of my other questions that follow, like which of my three m20 systems is the best baseline to build on; the space opera one, or the Fantasy Hack "fake" D&D one, or the DH5 custom one? Not that I expect any feedback from the peanut gallery, but if any comes in, I'll welcome it, and in the meantime I'll continue to weigh this in my own mind until I'm ready to decide and move forward.