Joseph it’s clear to me that the rambam didn’t c”v mean to say that a wife should treat her husband like a master in her. -actions-. Do you think he was trying to fix men up with lifelong slaves? That makes me shudder!
What he meant was that this is the way that a wife should treat her husband in her heart! That she should respect and admire him to such extent that he’ll be a like a king in her eyes.
If a wife feel that way towards her husband in her heart, I’d imagine serving him drinks might be one way she’d express that feeling.
But if a wife is -required- to serve her husband drinks, and is not doing so as a result of her admiration of him, the only thing she’ll be thinking is “I’d like to spill this on his head”. And that’s the only thing you might achieve from asking woman to serve drinks and open doors.