i think you should be able to replace individual parts like if you broke a driveline you could replace that without fixing the whole thing
Planned. Just like moving the car, dragging the car, more modular parts etc. There is a lot going into this!
This is something I've wanted for quite a while but one problem I can think of pretty quick is that, for example, the whole front of the car could be pushed in and when you replace the bumper, it just appears in the air in front of the crumpled car, or even worse, you replace the driveshaft and it appears inside of a part that's been damaged to hang in the way. It seems very hard to implement, but hopefully they will get it in someday.
I would like to see being able to take off part with out repairing the car. like if you are in cockpit view and your hood comes up I think you should be able to take it off. I'm not a fan of putting parts back on because of the reason above. It would be cool to be able to put on/change parts depending on what damage you have. (If that's possible.) It would be cool for the people who want it. But then again if you don't like that then don't use it that way.
But steering should be something you should be able to fix... If you have a derby car that the frame stays relatively straight on in the front end, and you lose steering in both tires, it's suck to have to throw away a good car just because you cant' replace the steering :\ And it'd be too expensive to fix a car totally just to derby it if it already has one run on it.