>> What could possibly go wrong?
Nothing. There are hardly any firewalls between ECUs. Firewalls do not exist on CAN.
The article is written by someone with no insight in car architecture :
>> First, however, carmakers must deploy more open OS platforms
Nothing to do with the reflashing
>> remove hardened firewalls between vehicle ECUs
There aren't any firewalls
>> and deploy networking topologies such as Ethernet, with proven security.
Ethernet is already widely deployed in cars for data hungry applications ( infotainment) For other uses, ethernet is absolutely not suitable ( price, power, wiring constraints, EMC, safety, .....)