I love the livery designer and the fact that you can copy layers between cars is great. It would be much improved if you could copy multiple layers (or your whole design at once) between cars rather than just one layer at a time, this would be a huge time saver.
I would personally love to be able to have the Paint colour be the same down the train. It’s really hard to find the correct colour for all of the shapes and coaches.
Yes, Matt said hex code is coming out in the next livery designer update (seen on roadmap). I believe he also said a mirror function will be coming as well. That will be really helpful!