As someone who rode for 19 years in Seattle, and rode through the very wet winters, here are a couple contrasting points of view.
First, there's no way you can get a decent tire diameter and also have fenders that run under the brake calipers. You only have two solutions: use short fenders that don't go under (like the SKS Raceblades) or use full fenders with a device like the River City ReachOvers that lets you interrupt the fender briefly at the brake bridge or fork crown and then continues it on the other side. There's a slight gap that gets dirty but the point of fenders is mostly to keep you dry. You can use Blackburn rack mounting straps (free at any bike shop because they usually have a bunch of them left over from rack installations) to make your own ReachOvers with just the right geometry.
Bear in mind that a full-fender installation is a pain if you don't have threaded studs on your chain stay and seat stay bridges, plus fender eyelets on the fork and seat stays. You have to use P-clamps at that point and those collect dirt, wear your finish, and so on. Fenders aren't readily a half-way proposition.
Second, most of the dirt and water isn't what the fenders intercept but rather the stuff that flies up from the road. Get some Buddyflaps long enough to get to within a couple inches of the ground when mounted on your fenders. They make a huge difference.
I've used rigid full-length fenders on several bikes and frankly, my best winter bike ever was a single-speed cross bike with mini-V brakes and big 35 mm full-length SKS fenders. I loved that bike for winter use. It was highly protective, kept clean, and simply worked. Definitely consider something like that. It can be a really cheap frame as long as it has the fender mounts everywhere.
I really appreciate your detailed info. The research definitely put me in thinking to get a steel "real winter" bike with fender mounts and space to fit wider tires. BUT to be honest I don't need a perfect solution and I know it won't be perfect. Still, it would be great to have fenders.
Since you have a lot of experience with riding in wet conditions, would you mind sharing what your favorite overshoes are? I know that there is no such thing as waterproof overshoes, still there are better and worse options out there. Thanks.