Wow. You are facing the exact same concern I am. At the end of this month, I will be traveling from New York to California via a moving truck with all my belongings AND my animals. As you can see from my signature below, I have a few of them to be concerned with during the trip. Its about a 3 - 4 day trip. As for the BPs specifically, I feel they are the ones of least concern to me. I plan to put them all in individual pillow cases (lowest thread count possible so the pillow case allows for more air) in an open box with a pillow at the bottom (to absorb the bumps) and have them ride with me in the cabin and not in the back with the furniture. I plan to let them out of their bags every day for a breather and have a water bowl available for them. I think the water bowl may be a waste of time as I dont think they will drink water as I am holding them. Putting them back in their enclosure to drink will be impractical as I dont plan to stop for more than an hour for breaks (I'll have a co-driver with me) and their enclosures (ranging from 35 to 75 gallon tanks) will be stored in the back. I do have plastic bins that I use to feed them at home so I'll likely use that to attempt giving them water while I'm at a pit stop. I'm not worried about the heat or humidity since I'll be traveling at the beginning of the summer so the temperature and humidity should be fine. BUT, just in case, I did buy those small hand warmers that I'll place under the pillow so they'll get some belly heat if needed. My vet says my plan should work just fine for a few days. I plan to skip a feeding the week before the move. I would hate for one of them to poop or throw up from nervousness in their bag but just in case, I do have back up pillow cases.
Thats pretty much my plan for my BPs. I have similar arrangement for my other critters but that's a different story. Hope this helped. Good luck. Please let us know what you finally decided to do.