Other things to consider, have a wall and door between the shop and
the garage. This will help keep the wood dust off the cars.

I concur; however configure that wall with some big doors (maybe pocket
doors?) so that the car bays can be used for extra in/out feed space for
table saw or other tool. (how often do you really need to rip a 12' board?

As to heat, I think that wood as a sole source of heat is a terrible idea in
Wisconsin. As a suppliment, go for it if codes will allow. You will probably
want to keep the shop at am "decent" ambient temp (40? 50?) in the dead of
winter so that you can go out there and work without waiting too long for
everything to warm up. You can really do that with wood.

I live in Northern NY (same climate). My shop used to be in an unheated
garage. The shop simply shut down at Thanksgiving. At the edges of the
woodworking season it was really unpleasant to work with 35-degree tools.

-Steve