Right, I think the Dark Age Warrior thing is probably not very useful historically very far outside the Dark Ages (though it surely works just fine in fantasy!) These might soak up a lot of spare bits for Dark Age and fantasy gamers, though, especially since I have a feeling that's the sort of bits that are in a lot of bit boxes out there - mostly because the amount of crossover between the Dark Ages historical and fantasy markets must surely encourage the production of lots of these sorts of kits, with lots of leftover bits!
Outside the Dark Ages, things begin getting more specific, and that does get tricky.
I expect some generic fatigues and combat boots with webbing, and some generic greatcoats with combat boots and webbing, would cover a lot of Victorian to 21st Century subjects for historical gamers who are willing to fudge accuracy a little, and work as well for sci-fi gaming as well.
Generic combat torsos with modern combat armor might begin limiting the historical use to the late 20th century and beyond, but Starship Troopers and Aliens pretty much runs on that sort of thing, and might have a market there. (I'd classify that loosely as "cyberpunk", and would probably cross over loosely with whatever market that has,to.)
I think the torsos from WA's Late Roman Legionaries set might be broadly useful: to my eye, it looks fine for many Dark Ages purposes, and as such works in fantasy. For ancients gaming, it has its uses for late Romans, naturally, but surely also works for mercenaries and barbarians as well, and might even be pushed back a little ways in time, for historical gamers who don't mind a little anachronism here and there. These Late Roman torsos also look to me like the foundation for a fine Death Fields faction - jast add Death Fields sci-fi bits or Accessory Sprues to complete the look. The "Space Roman" thing also seemed to be a recurring trope in pulp sci-fi, going back a long way (it was recognizable enough that Loony Toons' Marvin the Martian made sense to contemporary audiences as a parody!)
A body wearing loose trousers and a long, loose tunic with sandals, crude shoes, or even bare feet might cover a lot of odd Victorian-20th Century historical subjects, as that seems to have been the "uniform of choice" for those without a choice in impoverished, colonized places around the "third world", and thus plausible, I expect, for a lot of understandably disgruntled guerilla armies and such. I expect this sort of costume work well enough with just about anything from scimitars and machetes to AK-47s and RPGs, though suitable heads for any paticular subject might be a bit trickier to source (I don't think there are mountains of spare turbans, keffiyehs, boonie hats, kufis, rice hats, fezes and the like sitting around out there, while most of the bare heads in my stash of bits look decidedly northern and western European, and maybe a bit hard to fudge convincingly into use elsewhere!) Unfortunately, I can't think of more than niche uses in fantasy and sci-fi, but they can't all cross over, I guess.
For whatever it's worth, it seems to me that some of the more versatile torsos in WA's lineup might include:
- Persian Infantry - with long loose shirts and trousers, with a rope belt, and crude shoes; if I didn't know what army they're meant to be for, I'd have a hard time placing them in any particular century or continent - only the rope belts and hand-made moccasins (and, in a couple cases, some odd cloth armor) really limit their use very far into the modern era. And, of course, they would work fine for fantasy gamers.
- Late Roman Legionaries - pretty much the generic Dark Age chainmail torsos - could likely be mixed with pretty much any Dark Age arms and heads, and of course work fine for fantasy gamers.
- WA's "Great War" and "World Ablaze" line - the French, British, Italians, and Germans seem like they could span a few decades befor and after their time, when mixed with different heads and weapons, to create assorted armies from the Victorian era to at least early WWII. I've seen the French great-coats used in a couple odd projects today, such as pulp sci-fi WWII Germans, and I'm sure they could find more historical, pulp, and sci-fi uses, the British seem like they can cover Victorian historical and Victorian sci-fi/Steampunk subjects in addition to their "proper' use. The German, French, and Italian torsos and other bits seem like they can be mixed-and-matched to create other European armies (I believe Austrians and Polish seemed plausible, for example.)
- Panzer Lehr Division - the classic bad-guy uniform; useful for WWII Germans (and I'm sure there are lots of spare WWII German bits for them), and they certainly wouldn't look out of place in many sci-fi settings (Iron-Core seems to run on this theme, and with a little creativity they can be souped up into "Star Wars Imperial" style villains.
- French Partisans - a niche item, perhaps, but the costumes cover a lot of early 20th Century ground, and I've been using them for pulp investigators, gangster thugs, and cultists, and some of the torsos mix well with western gunslinger bits for pulp adventurer and late wild west and Weird West uses.
- Cannon Fodder - the fairly nondescript jumpsuits and boots could fit into a number of utilitarian contexts ranging from the mid-late 20th century, to all sorts of sci-fi (especially the more dystopian sorts!)
Of these, the Persians seem to me the most surprisingly useful, and the Romans the most obviously useful, with the rest being far more niche than the Persians and Romans. (YMMV)