What from the past would you most like to see eye-witness documentary footage of? For example, what if someone had been documenting the 40-year wanderings of the Hebrews through the desert? Perhaps Joshua would be the filmmaker, and after half a lifetime of filming he would catch the back of Moses, exhausted but invigorated by the sight of the Promised Land, stretching forward with one hand as he slumps over. The camera remains steady on the Land of Milk & Honey as the sun is rising, then pans down to the lifeless pile of robes. Camera lingers for perhaps a bit too long while Joshua begins a voice-over, expressing his mixed feelings about succeeding Moses.
I would also love to see footage of the first Roman Legions exploring the Great Britain, what was once a "dark place of the earth," according to Marlowe in Heart of Darkness. Trading and warfare with Celts, Druidic rituals... Stonehenge when it still looked new!