It can be used to maximize heal from sleep if your characters can coordinate it.
Hit points (PHB 196, highlighted in bold to highlight):
Hit points represent a combination of physical and mental durability.
the will to live and happiness. (…) This number often changes as
Creature takes damage or receives healing.
Getting hit points is healing.
Rest (PHB 186):
When the rest is interrupted by a period of strenuous activity – at least
Run, fight, cast spells or experience similar adventures for 1 hour
Activity – The characters have to start the rest again to benefit.
At the end
The character receives hit points that correspond to the total.
So resting is healing, and Beacon of Hope doesn't interrupt the rest.
Each target (..) receives the maximum number of hits for the duration
Points possible from every healing.
So Beacon of Hope can be used to maximize the healing of the hit dice for the rest of the group.
However, keep in mind that this requires a form of time coordination that not every DM would consider feasible or plausible due to the necessary understanding from the character's point of view and his knowledge of the (mechanics of the) world.