Your idea is fantastic and I would love to provide you with a solution that you can rely on and can build your business and even a company around it.
The flow can be as following:
1. Users will list their vehicles.
2. People will post bids on how much they can pay for it.
3. If the car is sold it will be listed as getting prepared for re-selling and description will be there like: This vehicle needs a change of paint, change of engine, seating is getting changed etc.
4. Other people who are interested in getting the vehicle when it renovated will post bids on it to purchase it when it is renovated.
This is just a rough sketch which I have in mind and can be polished further as you are the person with expertise and knowledge of the market.
This sounds like a plan to me.
Let's get in touch to discuss this in detail.
Thank you.