Could you then force the player to fast travel twice, once within the same worldspace to force time to pass, and then again to the new worldspace?
Exactly. Indeed you could use a moveto for the first travel, to ensure that a unexpected circumsance didn't make that fasttravel make the time pass.
thie means From A ( worldspace A ) to B (Tamriel) to C ( Tamriel ) to D ( Worldspace D ) making two load screens happen and lot longer time to load ... and not sure if is even worth ... why they just coudlnt' enable pcsetsleep ...
More like From A to A (just to make time pass) and then to B. But yes, this would be easier should they have include a function to force sleep.