Basically, we can have roads through the neutral territories if there is just one territory between 2 Trading Posts. If I have a neutral territory between 2 territories of mine with the Trading posts, I think the road should be of the highest quality that I have researched. Maybe if the roads are between different empires (do such things exist, actually?), the quality of these roads can be the lower between the two empires, but if my empire decided to connect 2 territories of mine with a road, I want that road to be fast! The mobility is already very sad whenever you play anyone but necrophages, especially when you have faction quest objectives 6-10 turns away from you, making neutral roads useless is just too much punishment for no clear reason