I played in a cover band last year that did this same thing. They either retuned or changed guitars every 2-3 songs. We played everything 1/2-step down as well.
I never touched my headstock/tuners during a show. I have an Eventide Pitchfactor, which, if run 100% wet, acts as a detuner. With a single-click turn of a knob, I can go up and down in half-step increments. Of course, this changes the tuning of all four strings, which I liked, because I was never a drop-tuner. It doesn't muck up the tone of my bass, either.
I changed guitars to my 5-string for 4 songs, along with the two guitarists, but other than that, I just adjusted the Pitchfactor to the key they played in and it was great. For people in the audience, nothing is worse than watching and listening to the band tuning their instruments between songs. If I ever play in another cover band,
the Pitchfactor will be right there with me; it's a must for that type of situation.