Definitely a nice historical overlap between the Wild West, Gaslight/Gothic Horror, the Victorian era, and Victorian Sci-Fi/steampunk, and that's an overlap that, I think, can be covered nicely with some nice, versatile miniature kits! And given that there's at least some market for each of these in various game settings.
The cowboys alone can cover more than just the North American Wild West - I expect that generic "cowboy" custumes themselves wouldn't be far out of place in most of the world through the Victorian era - shoes/boots, collared shirts, wastecoats and single-breasted jackets would have certainly been ubiquitous in the English-speaking world, and much of western Europe.
It's the Stetson hats, gun-belts, and six-shooters that make these characters "cowboys"... change the style of hat just a bit, and you've got Australians or New Zealanders to fight the various little wars from that part of the world. With or without different hats, the same basic "cowboy" figures would surely fit in just as well in South and Central America, Cuba, the Phillippines, South Africa and various English colonies in Africa and the Mideast, colonies in China and India, etc.
So, a nice "cowboy" kit with a large variety of different hats and bare heads - cowboy hats, outback hats, bowlers, top hats, gambler hats, flat caps, and the like would go a long way toward making this a versatile kit. From there, a nice selection of common rifles, revolvers, shotguns, and maybe knives and machetes would cover most common uses, I think.
An "accessory sprue" of e.g. heads with top hats-and-goggles, monocles, pneumatic steam-powered guns, tesla coils, plague-doctor masks, and all the other usual suspects would cover a mix of Victorian Sci-fi cliches, and the basis for a Death Fields faction in combination with the cowboys; if things like dynamite, picks and shovels, old-fashioned box cameras, lanterns, and the like can be fit onto the same sprue, it would also expand the usefulness of the "cowboys" set into prospectors and civilians....
A US army/cavalry set might cover a lot of ground as well, given the right selection of hats: if I'm not mistaken, the same uniforms could be painted blue or grey for either side of the American Civil War, blue for the US cavalry and other soldiers in the western territories through the "wild west" and various "Indian" Wars, and (I think?) khaki for campaigns in e.g. Cuba, China, the Phillipines....
Some loose, simple trousers and tunics or shirts with simple shoes or sandals, with only small variations, seem like they've been the "uniform of choice" for impoverised rebels, freedom-fighters, bandits, civilian "peasants", and the like for much of the world through the Victorian era into the 20th Century (illustrations above from Philippino and Cuban revolutions in the 1890s) - given a selection of different bare heads, straw hats, rice hats, boonie hats, sombreros, fezes, turbans, and so on to customize them with, and arm them up with old percussion rifles and revolvers, machetes, clubs, and whatever else these poorly-funded ad-hoc war bands might have been able arm themselves with, and you've got local fighters from colonies in Africa, Latin America, India, China, the Mideast, and elsewhere.
Beyond that, some of the more specific subjects that might be covered might include....
- "Indian" Wars: Native Americans
- I get the impression this subject is "niche" enough that a "generic plains Indians" sort of theme that covers as much ground a possible without being too specific might work best.
- New Zealand Wars: Maori warriors
- (I take it the colonial New Zealanders had a mix of British uniforms, and a pretty strange mix of uniforms for the local militias, comparable to some of the more eccentric uniforms in the American Civil War; the Australian/New Zealand faction of this war might be covered with a mix of Victorian British soldiers, ACW Zouaves, and "cowboys", with suitable outback hats)
- American Civil War: geneic ACW Zouaves
- There was such a bewildering variety of weird militia uniforms in this category, they can't all be covered, but some fairly representative torsoes and a variety of different hats/caps, with generic ACW rifles, sabres, and handguns, could cover a lot of ground for American and probably Canadian, Australian, New Zealand, and South African militias of the mid-1800s. This might be "niche", I'm sure I see the subject mentioned by ACW gamers.
- Spanish-American War: Spanish Army
- I think Americans could be improvised from American Civil War soldiers, but I have a feeling there isn't very much out there that would stand-in for the Spanish; I suspect the Spanish uniforms ca. 1890s probably looked similar enough to those of other western European nations that a selection of different hats and an appropriate paint scheme might be all it takes to adapt Spanish soldiers to different countries. (Otherwise, I think ACW soldiers and the Napoleonic British Riflemen might be improvised, with a lot of handwaving, but a set of fairly geneic European soldiers from the late 1800s might cover a lot of ground in this range!)
- Boer Wars: (Boers could be covered with "cowboys", and the British of the era should be pretty well covered by WA's other products)
- Crimean War: Russians, Ottomans
- European and other Colonial armies (Wherever a "generic" army won't work, it seems like the British, Spanish, Dutch, Italians, Portuguese, and French were involved in shenanigans around the world,and could use some Colonial Conquest armies.... )
- Sino-Japanese War etc.: Japanese, Qing Chinese, Joseon Koreans
- South American armies (Peru and Venezuela alone seem to have participated in dozens of revolutions, rebellions, civil wars, and border wars between them in the latter half of the 19th century! Maybe a niche subject, but it seems like a fascinating period of history that probably has had zero coverage in wargaming.)
- African armies: Zulus might be well-covered by other manufacturers, but maybe the Mahdist and Asante empires might be some great subjects for this era and continent?
I think a lot of the above can find their ways into projects for various historical and pulp adventure/sci-fi subjects from the 1800s up to maybe the 1930s, with only a little imagination, and they could probably find their way into fantasy projects as well, with the main question being whether there are enough gamers interested in these subjects to make them worth developing.
(For my part, I'd definitely be interested in the Wild West subjects, and anything I might be able to use for VSF and pulp sci-fi/horror gaming, but I always have trouble gauging what might go over well with "mainstream" historical and fantasy gamers, so I wonder what they can do with the above?)