Another vote for the Pnuma vest. The battery location is kind of in the same area of the waist belt of the saddle, but you can move it above or below the belt when you are tightening it. I haven't found it to be an issue.
It works best for me to wear a thin t shirt, then the vest to get the heat as close to my skin as possible. Then I wear a merino base layer, the furnace, to keep the heat trapped in. Works excellent, I have been thrilled with this system every time I use it. Once I start to get cold I turn it on high & it warms me right up, especially helps with my fingers & toes. I do have an extra battery & charger which is nice but I wouldn't say necessary. One battery can get me through a morning & evening hunt.
I haven't tried the pants yet but would assume they are just as great!