<insert something I've probably said in other threads about colonialism in D&D and about B2>
Anyway, here's the idea I floated as a temporary game for my current group while our GM preps the next arc, based on the Goodman reissue of B1 and B2 for 5e with a splash of B/X and Dying Earth. Waiting to hear back from them:
The ages have shifted under the red moonless sky and the forces of "Law" are split into Order, Justice, and Mercy, and the forces of "Chaos" into Aberration, Immortality (aka Undeath), and Temptation, with a plethora of saints, devils, spirits and whatnot making pacts and answer prayers, but no gods. And with a lot of "people" just wishing they'd leave them alone. The pelgranes and sandestins of past ages have mostly been hunted to extinction. Of particular note, the forces of extreme Law along the border are being championed by humano-supremacists (with demi-humans being "ok").
The party members could be anything from Kobolds to Warforged (have the Volo, Eberron, Ravnica, and Tortle races), either "civilized" or not so much, and are racing to the newly opened Borderlands to recover objects and accomplish missions before other competing groups of various motivations do so. Some magical disguises to start with might aid in a bit of infiltration or just getting along when needed, although some of the party might chafe at altering their usual smells, diets, and accents.
[DMs note: "People" includes the humanoids. And of course the people in the keep, B1 area, and B2 area all have varying motivations too -- with many of those running the Keep not being particularly any "better" than some in the back left corner of the caves, for example, and being notably much worse than some of the inhabitants of other parts of the caves.]