Walk without rythm, and the worm cannot find you… nor can moderators.
Your lighting problem sounds like an auto-iris /exposure problem. All cameras should be run on manual focus and manual iris for a job like that, pre-white balanced before the colored stage lighting goes on, then just leave the colors as the LD intended them. Sometimes you can get the lighting man to leave up a minimal base level of white light, enough to keep the camera shots from getting too grainy from having to boost gain. But modern cameras are much more sensitive than when I used to do this sort of thing using tube cameras and early CCD’s
Whether you want to live-switch the show and just tidy up in post, or just shoot 3 cameras all iso and then replicate the live switch in post, you should probably rent the right cameras for this, and the rental shop will tell you what they have that’s the best fit . Classically, you’d have two cameras right and left, plus one halfway back of the house or more, shooting coverage on a wide-shot, that one will want the longest lens and sturdiest tripod, and best low-light ability because of the distance, and the extra stop or two lost for the longer lens. A fourth cam would rove behind and onstage and in the front row. You could actually do a pretty good job with just two, if they were very coordinated and each one covered well while the other moved and got their next shot, using radio intercoms, noise-free headsets and a director watching their shots. But that’s tough even for pros. More cameras = more safety, flexibility and reliability. When Idid the multicam iso thing in the field, I and my partner had a pre-decided set of rules for who would shoot what, and an agreed set of hand signals to each other for who was/wanted to go tight or wide at any moment. Takes some coordination!
Tip: shoot the rehearsal end to end, and do most of that with the cameras right onstage and close-up, particularly the lead singer and drummer. You may be able to inter-cut this later and look like you had six cameras, plus then you don’t have to ruin the crowd’s experience of the band during the actual show with cameramen on stage. Don’t forget to get plenty of b-roll reaction shots of band members and crowd to cover edits.
You would want to run the board mix into one channel of each camcorder to help you out later. The other channel can be the onboard mic for use as a scratch track and maybe for extra crowd effects later.
Don’t be sanguine about trusting the audio recording to some venue guy sight unseen, no matter how experienced he is. One reason is, the guy mixing for the house is tailoring his mix so it sounds good in the room full of noisy people with the speakers and geometry of the live space. If those same settings make a good sound for a TV recording as well, it would be a big coincidence. Just one aspect of that would be how much the drums are mic’ed, for example. You could wind up with a very thin drum section if not careful. So you need to talk these aspects over with the sound guy ahead of time, maybe cover your bets by placing an independent recorder and stereo pair somewhere on or near center stage for an alternate pickup point. Also, be sure your recordings are not too hot or too low level-wise: use matching transformers or keep everything on line level, with a pad standing by.