The casseroll and the hillborne are spot on for your purposes. I would also check out some cross bikes. Not as upright perhaps (depending on the model) but loads of fun as a road bike. You can run pretty fat tires and they generally have eyelets. They also have more forgiving giving since they generally have a compact crank. I really like my Soma doublecross and I built it with a triple chainring so it offers a real alternative to my racing bike. I built the bike up from bits and pieces from different donor bikes (sort of like you are thinking of doing):
