I've had more time on a Classic, but I own both so I'll chime in......
1) 2011 / 2012 Voyagers: Still run hot? Still pop on deceleration? Still resist tweaking, such as the Big3 application?....
We'll let the more experienced answer this one, but if you search here there's a lot of tweaks that can be done.
2) Does the Vaquero saddle fit the Voyager properly?
I'm in the same boat as you. I wanted a Vaquero, but with the leg fairings, bigger seat, and taller shield. I decided to go with a Voyager from the start. In the process I learned a bit about the seats as I wanted to move the Russell from my Classic over to my next bike. I think the Voyager and Vaquero are going to be different, not by much... but enough to make the mod difficult. There's a rear latch that is fit differently on the 1700 bikes, depending on the model. That's not so much a big deal, but fit still wasn't possible. I bought all of the needed seat brackets and locks to move a Classic seat to the Voyager and the issue was with the Voyager chrome. It's very tall and the Voyager seat frame is made different. I'll wager that (even if you change brackets) that the seat won't lock in properly. I may be wrong, but from what I can tell it is the Nomad and the Voyager that are compatible in swap because they have the same chrome around the seat area.
3) I'd like to make the Tourpack a quick release system, because it will be off almost all the time. If anyone has done it, can they please weigh in?
I don't think that there is a bolt on quick release for the Tourpack. Also, I don't think that you can even use a Vaquero set-up. I think you have to go with the Nomad backrest.
4) Am I crazy for going this route? I like the looks of the final result, but any advice is appreciated!
Keep looking, I've been trying to find a wrecked Nomad or a backrest for sale for 3 months. Nothing yet. I can say that I like the rear speakers and use the tourpack more than the side bags. Once you get going you don't notice it. With that, I'm not pushing to find the Nomad parts.