I liked all those suggestions you mention, plus there are others that fit general Death Fields or more broadly sci-fi description (and I've championed most, if not all, at one point or another!):
- Space Pirates
- Multi-Species Aliens (I think this is the sort of thing I've been calling "rubber forehead aliens": just different alien heads and arms to add to human bodies for those Star Wars and Star Trek style "guys in weird masks/makeup" look: even an Accessory Sprue of alien heads to add to existing and future Death Fields bodies would be great for this, if so!)
- Modular Robots (the cyborg bits from the "Death Fields Accessory Sprue #1" and upcoming "Cannon Fodder 2" set's renders look fantastic, and I bet some humanoid battle-droid "Not-Terminators" using bits like that would work great!)
- Sci-Fi civilians
- Cyberpunk Corporate Security (Cannon Fodder can cover this base, I think, especially kit-bashed with "Modern Military Generic Infantry" - a great historical/alt-history/cyberpunk subject as well!)
- "Apocalyptic Survivors", and the similar (but, I imagine, more heavily-armed and organized?) "Insurgent and Irregular Moderns" - both of which seem like natural opponents for those robots, generic modern military, and cyberpunk factions for post-apocalyptic or dystopican uprising against our cybernetic or corporate overlords!
The poll seems like it ended up favoring sci-fi: that's up to 7 or 8 of those 11 runners-up that could be at least loosely considered sci-fi, and maybe more, if you want to include the suggestion of those "Hooded/Robed Monks/Cultists" (for a slightly different flavor of speculative fiction!), and the winner, "Landsknecht Ogres" (as a Death Fields faction rather than fantasy, it seems?)
The space piraes seem like they'd be a lot of fun to kitbash from something, and the alien idea sounds like a ton of fun, too! (I combined some Oathmark orcs with some sci-fi weaponry for a similar idea - I think of them as being the villains of a Star Trek or Star Wars sort of space opera, who raid, loot and pillage colony worlds and unprepared starships as space pirates!)