I tried Nague's savegame and it really seems residents don't need access to industrial buildings for things to run smooth. But there's another issue that I think no one has come up with yet: as it is now, bus system is nothing but an exploit.
When you establish a bus line and spread your stops around, if it is has a useful path, some of those stops, due to some weird behavior, will be swarmed by hundreds of citizens (guess a lot of you already got it in their own cities or at least saw some pictures about that). If there was no buses, those citizens would be riding a car, increasing traffic intensity, but this way they will just stay in the stop until they despawn or get teleported.
So, bus system really takes people from roads, but in a completely wrong way.
Co needs to tells us something about this.