Sounds like you'd be best served by a monorail camera with clear detents on the zero positions and good levels on both front and rear standards. If you're working with primarily wideangle lenses, a bag bellows would be necessary. There are a number of good options available: Sinar, Arca Swiss, Linhof. You'd be trading off portability/compactness for this level of precision, but it sounds like a solution to your frustrations.