Gazelle is a premium brand with only 12 entries on known problems list. 3 are about a missing plug in the hydraulic brake leading to 3 or 4 warranty trips.
Understand if a used Gazelle needs a battery, Bosch batteries are about $1000. Don't understand your focus on mid-drives on Vancouver. Geared hub motors overheat on 1000' rise in an hour. Your island is not that big IMHO. I cross ~80 hills with my geared hub motor with 60 lb groceries on the uphill leg. I would insist on 500 w and 750 is better. But you're not planning to carry groceries. Besides my Army vet knee gives up sometimes, and I have to use a throttle those trips. Takes a week or two to heal up, and I don't keep a car.
Mid-drives, if you break a chain or a motor gear or something, you're in for a tow truck, or pushing a long way. I wore out gears in a hub motor, rode it out to property and back again 45 miles without power by pedaling. No drag. Plus Bosch warrenty service would be a week or more. You have to haul bike to warranty shop in a vehicle or push it. I had a spare hub motor in the garage & was back under power after 2 afternoons work. No tow truck required.