I have to disagree a bit.
With offices, we need three types of densities, not two. With industry, we need levels for specialization districts like farms that are already present for generic industry. What I would do is seperate generic industries into seperate specializations: clean (high-tech level 3), manufacturing (level 2) and dirty industries (level 1) like in SC4, but hopefully better executed. I'd also think about 3 density types for generic industries, I don't know WHY ON EARTH you're insisting on two densities, when you know perfectly well they aren't working well enough for residential/commercial zones.