I do something similar. I kind of beat them to the punch in the sense that I race to the power weapon, (for example a sas-12) and waste all but one shot. I then pick up my original weapon and continue with the game. I only do this when im up against people I KNOW rely heavily on PW's though
For me, I just switch to my pistol if the Power Weapon is my primary and I'm about to die. Makes them mad to see that my E3 Para 9 is there instead of an RPG or Hammer. And vice versa if I have a Pistole.