Well, messing with this bus (audio volume.. blinking displays etc) could be disruptive as well, but not as critical as killing the engine.
Was introduced as a cheaper alternative to CAN, and to be used for non-critical aspects of cars (intended). Though seat controls are listed as common use for it. Which with some occupants and cars with the seatbelt - would enable the seat to pull the driver away from the controls. So whilst not directly deemed critical - certainly a vector of concern in some permutations of seat/driver position (thinking large 4x4's driven by small people who end up having the seat fully forward and raised, as an example).
My initial concern was the main lights, though as you cleared that up to just internal lighting - that again could prove a problem as dark roads, a sudden change in internal lighting would from internal glare reduce visibility.
Biggest take away is that the LIN bus has no form of encryption and the only verification would be checksums upon the data packet.
I'm sure we will read more about LIN over the years as the ability for car makers to cut-corners is not unheard of and as LIN is cheaper to implement than CAM, can see how that may well play out.
Combine seat adjustment with GPS position reporting and you could devise a way to make a targeted person lose control, without taking control of "critical" systems, exactly as they're crossing a bridge.
Suddenly I feel the urge to Faraday-cage my car.