Hi, impersonating a pilot doesn't seem as smart plan, suppose you even manage to bring on board some kind of weapon, the same is possible to do anyway, but without calling much attention as uniformed pilot crew seating as passengers surely does.
Really beside movie-like plots I don't see what would be the advantage even you manage to bring a weapon
For the 67th time, all what is asked by most people here, is just to quit bothering flight crew, namely pilots. They are among the most trusted individual in the society and should be allowed to board with all the stuff that an human person may need or like when piloting for a work. Plenty of homemade food and protein drinks ? Sure. A leatherman in case they need to fix any gizmo or hotel door ? Yes. A beauty case full of all metalling thingies and creams to take proper care of your boy? Allowed.
And then if you want my most honest opinion, the same should be applied to passengers too.
Of course pilots would need to go under scanners and detectors just like pax, security would then have the possibility of giving a second look at any person or baggage, randomly or by any criteria.
Is this too much to ask ?