We have taken our Newfoundland on a couple of cross-country trips, and he loves the adventure, almost as much as the kids do!
On the few occasions where we have had to leave him alone in the RV, I've left the genset running and the AC running.
I don't worry about leaving the windows open when the dog is staying in the RV, since he pretty much scares away anybody that even looks in the windows. If he's crated, we cover all the windows to prevent looking in, but his bark still gets people's attention. That pretty much fixes the security concerns, for us anyway.
I too worry about the genset failing, but even in direct sun in Kansas summer time, the RV didn't heat up inside any quicker than the stick house does. I have no idea if our RV has more insulation than others, but it holds the heat just fine in sub-zero weather as well.
We've had this Newf on a 6K mile trip and an 11K mile trip, and never had a problem. Ok, there was this one time, but it wasn't related to anything we're talking about now. :)