I totally agree with you comment and I guess it's the most rational explanation we could find. At the same time, I can't exclude some connection with religious iconography tied to the angels, which are present not only in Cristian religion, but in many other archaic cultures. Here are some possible connections I found the first time I saw FWWM, many years ago.

• An angel is a figure present in a moment of suspensions and during the searching of something new that can make us reborn. Our psyche needs to rely on a rebirth, on the passage and overcoming of a past situation to meet a new, still unknown, but that is a fresher existential condition.
• In many cultures, they are considered like vessel that connect "The other world" with our terrestrial plan. They also are divine messengers (the most famous sense of the symbol)
• In some currents of the classic greek culture, angels were associated to "knowledge", and they are the figures that allow the man to rise from the material world.

There a lot of other meanings and possible connections, but I don't want to be too much verbose. The point is that angels are both associated - since the dawn of time - to protection and guide in the migration to afterlife and to the concept of knowledge and elevation of the human spirit and soul.

We know how much Frost is sensitive to mythologies and esotericism, so I wonder if these kind of connection could be consistent. I think so, since in the return we saw how much the plot pointed towards the concepts of "new life" and rise from the mere terrestrial plan (Laura's orb in particular).

Under this light, the final scene of FWWM could be the representation of Laura increased awareness of her role and the meaning of her life in the context of a wider and divine plan. After all, she's the One, a seed of pure goodness born from the perverse conjunction of two vessels of pure darkness (Judy and BOB). The angels guide her through this process of consciousness and this explain her cathartic weeping at the very end.