If this is the minecraft world you want, then why bother sleeping at all? If it's just to have a monster rich yet phantom-less world, then sleeping once every 3 days will give you that. I honestly fail to see what purpose this bit of 'realism' serves the game, when you can get what you're after simply by not sleeping.
If we wish to be realistic, why doesn't the player suffer fatigue penalties when not sleeping? Why can the player effectively sleep for slightly more than half of the day/night cycle? Why don't villages and players snore while sleeping? Why don't players dream? Why isn't there a unique, dreamtime world, unique from the Overworld, Nether or The End?
I am genuinely failing to see how this feature is in any way 'essential'. What am I missing? Why do you consider mob generation while sleeping to be essential?