Dunno if you considered my idea or not, but modifying military figures into civilians is actually pretty easy with a bit of knife and putty-work, much easier than the other way around, for sure... Shave off insignia and epaulettes with the knife, make soft-caps to replace helmets with a bit of putty and sheet plastic for a bill or brim, and "hair" for bare heads outta putty, un-blouse trousers with putty "pantlegs", and painting jackets and trousers in "civilian" colors, like a dark blue jacket, tan pants, maybe a red & white polka-dotted scarf here or there... One guy with a Russian "bear hat" and a PPSh would establish their nationality in a heartbeat, and the Partisan-connection could be the mix of PPShs,Mosin Nagants, K-98s, and MP-40s. Partisans used whatever weapons and ammo they could scrounge up, and using military personal equipment from both sides was the norm... Even sex-changes are fairly easy, especially with the bulky clothing worn in Russia during the inclement weather.. Just takes a ittle putty-work on the hair, really... One could do Chetniks as well..
Learning how to convert figures is a necessity for the diorama builder... That way you're never tied to making the story fit your figures... You've got a good idea, and it's not a common one... I'd say, "run with it"... You could even model it as a crash-landing with the pilot being taken prisoner by the Partisans, with a dead gunner, or vice-versa... I think it would be a helluva dramatic scene, since being captured by the Russians was bad enough for the Germans, but to be captured by armed civilians, in the middle of nowhere, right after your unit hit targets in the area? (Shudder) Better hope the military gets to you soon...