When making a class 101 in BR Green I had to make the BR logo with the tools there so what I want to suggest is having logos for TOCs in the livery designer as that would make it nicer, than a shoddy logo made by me.
the issue with this is they need to get licences to allow this which i don't think they can which is why it's not a thing
That is indeed the problem. Companies don't want people creating offensive or vulgar images with their logo besides it. That is also the reason you can't edit onto the standard livery. Even though I'd like to see placable logos, I completely understand why it isn't possible.
As said above, it will not happen due to licensing. However, if you're on PC you can install the logo pack mod.