If I were to design my perfect bed, it would have:
A small lip all the way around the top, just enough to hold the mattress in place without interfering with bed making.
I'd want to maximise the open space for storage underneath and keep it flexible without it being on display. Lots of ways to do that, I'd also want easy access - I might not need that now, but who knows...
I'd like any side tables. draws, shelves, attached to the headboard rather than free standing, like in every hotel chain. Not only does it make hovering easier, seeing more floor gives the illusion of a bigger room.
Adjustable height, not much maybe 100mm, assuming it's the perfect height to start with, a change of mattress sometime in the future might need that height fine tuning.
There seems to be an assumption that it'll be made of tree, there are other materials available. I like working with box steel knock together systems, it's never wasted, you can always knock it apart and make something else.
I've in some way constructed most of the beds I've slept in, though they've either been modified beds or something repurposed. They've also all been low budget, not to save money, I've just never been sure enough about what I want or how likely it is I'll want to keep it long term.