healing only in a bed, but player enters a dream dimension

The idea is that players only regenerate health when sleeping, but lying in a bed for a few minutes isn´t fun at all. Instead they enter the "dream dimension but can still be attacked  by other players and mobs in the over world " .

• overworld is still loaded
• players wake up when attacked in the overworld
• players wake up when killed in the dream dimension
• players only heal while sleeping.

Some ideas what they can do in the dream dimension:

• Improve their healing
• some recipes are locked and can only be unlocked in the dream dimension.
• monsters nearby the players bed will cause "nightmares" (more) monsters will spawn in the dream dimension.

• players can get a buff for the next day

   

...or whatever you can think of. Point of the dream dimension is to keep the player vulnerable in the bed to heal without causing boredom.