Ian,
Drainage is often neglected in an accident repair or restoration. The consequences of that depend on how much rain the car sees, subsequently. But even in one drive in a downpour, a car with incorrect drainage car can take on water that can sit for a long time in the wrong places, invisibly, and do a lot of damage.
I'll refrain from making jokes about Vancouver and rain, but the questions you're asking are very wise. Pawel's document has a lot of useful info.
Meyer