Tom,, are these really solid wood or is only the cabinet front made of solid wood. When you look in the back of some "name brand" cabinets, you find that the carcasses are made of particle board and it's just the face frame and door that are solid. I'd be more than happy with plywood carcasses and the only way I know to get those is to make them or have them made.
The good news is that the toe kick board might be replaceable. Many of these are and you just pull them off. Check this before you get further into considering replacement materials. One clip on each side holds the toe kick boards on.