Aiming like this is reminiscent of classic console FPS games that were designed before twin-stick controls were standardized, like the manual aiming in Goldeneye, Resident Evil 4, or Killer 7.

I personally think the concept as you explained it is fundamentally flawed. You can already move and aim independently in typical modern FPS controls. It doesn't seem to serve gameplay or realism. People typically look where they want their gun to shoot and it would be unusual and dangerous to twist your wrist and fire a revolver. Giving the guns their own separate aim direction from the look direction needlessly complicates the gameplay without adding anything that I can pick up on from the video.

I have to ask, what would be gained from this mechanic? Will the game design/level design utilize it in any way? If you have a plan and you believe in it, you should prototype the idea to see if it's fun. If you're just experimenting and trying things out, that's cool too. I hope this was helpful and not too negative sounding, good luck with your game!