Any fan who cares enough to watch a fan edit will instantly know the difference between a Rebel X-Wing and a Resistance X-Wing, or an Imperial TIE Fighter and a First Order Tie Fighter. Admittedly in the latter case a simple color swap should fool most people, but that’d be incredibly tedious to accomplish. There’s definitely no way to make an imperial stormtrooper convincingly pass for a First Order stormtrooper.
Well, I’m assuming Gmatias wouldn’t be using shots that prominently have Imperial Stormtroopers. I think he’s just going to use shots of the Rebels running along the beach and stuff.
And you honestly can’t tell me you can discern the difference between the Rebels and the Resistance, fan or otherwise.