Well, I'm not a welder or a painter but I have a lot of ideas...
We've lived in India most of my daughter's life and she loves the three-wheeler taxis ("autorickshaws," originally trike-converted scooters, now a separate breed) almost as much as my bike or the scooter.
So the wife and I came up with a plan, based on the fact we never had those cool race car beds as kids. Worked with some guys I know who do custom motorcycle paint and bodywork/fabrication, and in the end, Sophie ended up sleeping in this:
It has internal and external lighting, a fan, and comes apart for transport. Got some small things to smooth out still, and it's probably not the paragon of child safety, but we're all digging it.
(And here, as purchased