I'm in my mid 20s and love the Crown Vic and it's brethren. It's the only full size, six passenger, rear wheel drive, V8, body-on-frame car still being produced since GM killed off the Caprice in the mid '90s. It's like a relic of the stone age by today's standards of vehicle design, but has become so refined that you would never know it uses the same basic design of a car from the 1950s. You simply can't find a simpler, more durable, more comfortable, more powerful, smoother riding car that gets around 25-30mpg. If you would rather have something front wheel drive that doesn't look like a police car, almost any midsize or full size car on the market should be able to fit a wheelchair in the trunk. The only way to know is to take a wheelchair with you when you go car shopping and see how it fits.
Another note about the Crown Vic: if I remember correctly, the trunk has a very deep well at the back of it that would probably accommodate a wheelchair, folded up, standing up. There is also a parcel shelf in front of the aforementioned well, where the spare tire sits, that has enough room for several grocery bags. A lot of elderly and/or handicapped people buy these cars, so it wouldn't surprise me if this is sort of a built in feature for this purpose. You might want to check this out.