I think it would be really cool to be able to play with assembly parts, I always liked this idea of assembling miniature planes and submarines, but I think something bigger could be done.
So my play would be to offer guided assembly projects for vintage car replicas, but realized in significantly larger sizes than the usual toys.
The toy car would be converted to electric operation.
After assembly, you would have a functional replica in a scale suitable for use by 8~10 year olds.