Currently, when you select “avoid highways”, highways are avoided at all cost. How about adding a option for"mild highway usage". This would allow the usage of short highway stretches (<10km) if they would mitigate sending you through the city or would save you tremendous time.
For example, I live near a highway and when I use navigation (with highways disabled), the app always wants to send me 7kms / 25mins through the city instead of routing me over the highway for 3kms.
While this case is not a big problem as I know the area, I usually just take the short highway stretch and then continue with the suggested route. However, when in an unknown area, it can easily happen that you take a long diversion instead of a short highway stretch. (Especially when the highway is the only way across a river in the area)