those garages need to be bigger
If he is using tall vehicles then yes, but most racing like vehicles in BL are low to the ground, so this is not important.
What I would do however is make the doors wider, they seem a bit to skinny.
I have also built garages for my racetracks, though I did it pretty differently to you. Here are some images for ideas and/ reference (hope you don't mind me posting these, I can remove if you like):

*NOT DONE*Love it so far though dude. Keen to see it done and to check it out!