I've taken a carbon fiber tenor ukulele in a gig bag on an aluminum frame bike.

I'm not sure if the intent is to eliminate your car some day, or let it sit for months without starting it up. If you are going to get rid of the car, then a nice trailer that can be used for multiple purposes and would probably be worth the investment.

If you are going to keep the car, then running it once a week might be better.

John