Another viewpoint is to consider the 35-70mm lens as a shift in quality rather than an upgrade or downgrade. F/FA lenses perform and render very differently compared to their DA siblings. Color rendering, contrast, sharpness, etc is very different. Remember that these lenses were designed with film as the target. What we see as color casts in the digital realm would come across as rich and saturated hues. It's kind of like going from an electric guitar to an acoustic guitar.
Go for it! You may discover something new in your journey.