Occupying the cabover bunk while driving is not a wise idea for a variety of reasons, both in terms of safety and structural soundness. This is something to bear in mind if "nonstop traveling" means having one person drive while others sleep.
There are both class C and class A motorhomes with bunks, which might work out better for your wants. It will be hard to find anything that doesn't look like some cross between an apartment and a sailboat cabin, though at least now there are a few options besides floral prints and vaguely southwestern patterns.
If you're handy and ambitious, you might be able to build something more like what you want, perhaps a (smallish) school bus conversion or a step van conversion. It is a lot of work.