Well, there’s bike racks, and there’s nothing keeping you from designing a vehicle like this:
RRRR+----\
H####|
----+----/
and inserting a bike in between the two trailing board sections and then racking it. It’s not perfect, but it’s possible.
I don’t intend to provide support for bike racks that can rack vehicles more than 1 tile wide, for various reasons involving the code being really complicated. Someone else is welcome to give it a try, though.
Some day, I plan to add support for flatbed carriers. However, that’s also going to be really hard for so many reasons, and I have to rewrite parts of the vehicle collision code first. I do plan to start work on the collision code rewrite Real Soon Now, but it’s still going to be a while.