Does any manufacturer do king beds right?

You might consider a decent sized toy hauler. Remove all the stuff in the rear and you would have good space to put your king size bed in there. You could get a simple frame and anchor it down, leaving storage underneath. Same for the nightstands.

Basically take out all the cheap RV furnishings and put in your own stuff.

There would likely be another bed or at least bunks that you could remove as well, and convert the space to whatever you want--pantry, desk, whatever.