If it Had to be Found Footage, let's do this *spoilers maybe*

I would have this treatment like this...

Scenario 1-
The soldier we see at the end of the film standing next to Stalin would be given his metal and time advances. We move into the present day now that Russia is no longer Communist. The government decides to reach into the archives of the KGB and release old documents and films regarding their activities. In an attempt to preserve this film, its secret is discovered. The new government decides to investigate. Meanwhile, there is a descendent of Frankenstein around who may or may not know of his heritage. There is a race against time to discover if the Soviet army did indeed destroy Frankenstein's Army.

Scenario 2-
We could have a descendent of Frankenstein working for the KGB in the office that handles old film footage taken during the war. In a project to restore old film, he finds the footage. Around this time, he discovers he legacy. He decides to honor his true legacy by returning to the old site and he finds the old records. He picks up from where his ancestor left off...

Or in the 2nd scenario, someone working for the KGB stumbles across the old footage and is an assistant of sorts to a descendant of Frankenstein, who happens to be a medical student. He knows Frankenstein is trying to discover the secret of life and thinks the doctor would be interested. In this footage, the young doctor learns many things. Once the young medical student finds the old ruins, he discovers the old papers...

I could do this from now until next week. One thing I know for sure, the camera would be stable during filming, that's for sure (LOL)!