On the one hand, I like the idea of organic random ambushes happening, as initially advertised; it would certainly add more dynamism to the world. On the other hand, it does seem like a gameplay mechanic that could get annoying - like the Batmobile missions in Arkham Knight.
As someone mentioned above, there are actually a good number of scripted chase events, even though they're not entirely satisfying. And yeah, the way the game's built the cars aren't ideal for driving and shooting. Depending on what multiplayer looks like (mostly co-op missions, I hope), chases could be much more common. For that matter, I think a lot of the cut features could be implemented with multiplayer (not that that's the point, sorry for bringing it up).