I was really hoping that this could be done in UE4.
If I paid your counselling expenses could you have another go at it?
UPDATE: Dunno if you’ve seen “Sea of Thieves” but it uses the UE4 engine and I tried out the closed beta this weekend and they’ve pretty much pulled it off. The ships you can crew with your online friends moved about in the world yet you can move around on board as though you’re on solid ground.