No, you don't have to be rooted to side-load, that's why I was thinking about it. I've never rooted anything and didn't want to go down that rabbit hole. There's tons of info in the Nexus 6 forums on XDA, it seems pretty easy and straightforward. Just read through everything and then read it again.
You can also force an update over wifi without your SIM card in, but it's not the exact Verizon version. I thought about doing that too.
The catch, of course, is that you'd have to manually update every time as it looks like, right now anyway, Verizon is never going to play nice. Jerks. I love their coverage but really, I mostly hate them.