Since users are going to want to continue having Bluetooth access and other device linked to their car, connectivity is not going to go away. When Bluetooth first came out in cars, hackers found ways to control and effect these cars quite easily.
Most of the wireless vulnerabilities that allow an attacker to control aspects of a vehicle are found in add-on components that are directly connected to the vehicle's CANbus via the OBD-II port. Insecure IoT-like GPS devices handed out by insurance firms, for example. There are few models where there was a successful remote attack (with the ability to control throttle, brakes, etc) without any such insecure add-ons. Mainly this happened with Chrysler products. Even then I can't think of any cases off the top of my head where Bluetooth was the attack vector. In both scenarios the connection was cellular, for the cases I read about. With that being said:
The way they currently have their networks set up is stupid and dangerous. As stated in the article above, you need two separate networks. I believe they could be linked with one-way connections at points. You could potentially solve the add-on component issue by making two physical OBD connectors, one which offers only one-way data (consumer-facing) and a secure two-way one for temporary use (wired!) during updates/repair work. So even if you have an insecure GPS module or other wireless device hooked up to the one-way port, it can only receive data and can't feed anything back into the secure network.
Ditto with BT/infotainment systems. There's no need to remove BT. Just isolate that system so that your phone can link and play media, run apps, whatever - without the ability to transmit to the driving systems. Again, the core driving systems should be isolated such that they can share data outside their network but only receive data from other secured systems including their sensors. No influence from outside.