The physical process of piling up pillows may be a problem. The people will need to pile up the pillows in a pyramid like shape and the process of stacking may determine how stable it the stack is while people are passing pillows up the stack to the top, as well as how well the stack of pillows cushions the protagonist when he jumps.
Did you ever hear of the Bent Pyramid?
The Bent Pyramid is an ancient Egyptian pyramid located at the royal necropolis of Dahshur, approximately 40 kilometres south of Cairo, built under the Old Kingdom Pharaoh Sneferu (c. 2600 BC). A unique example of early pyramid development in Egypt, this was the second pyramid built by Sneferu.
The Bent Pyramid rises from the desert at a 54-degree inclination, but the top section (above 47 metres) is built at the shallower angle of 43 degrees, lending the pyramid its very obvious 'bent' appearance.
Archaeologists now believe that the Bent Pyramid represents a transitional form between step-sided and smooth-sided pyramids (see Step pyramid). It has been suggested that due to the steepness of the original angle of inclination the structure may have begun to show signs of instability during construction, forcing the builders to adopt a shallower angle to avert the structure's collapse. This theory appears to be borne out by the fact that the adjacent Red Pyramid, built immediately afterwards by the same Pharaoh, was constructed at an angle of 43 degrees from its base. This fact also contradicts the theory that at the initial angle the construction would take too long because Sneferu's death was nearing, so the builders changed the angle to complete the construction in time. In 1974 Kurt Mendelssohn suggested the change of the angle to have been made as a security precaution in reaction to a catastrophic collapse of the Meidum Pyramid while it was still under construction.
The outer casing and much of the structure of the Maidum Pyramid collapsed sometime during the period of ancient Egypt, possibly while it was still being built.
The collapse of this pyramid during the reign of Sneferu is the likely reason for the change from 54 to 43 degrees of his second pyramid at Dahshur, the Bent Pyramid.3
the Maidum Pyramid is made out of rocks, and yet it collapsed. Obviusly a pyramid made out of soft and flexible pillows would have a much greater tendency to shift and thus collapse and would have to be built much more carefully.
You may remember the fairy tale of "The Princess and the Pea":
The story tells of a prince who wants to marry a princess but is having difficulty finding a suitable wife. Something is always wrong with those he meets and he cannot be certain they are real princesses because they have bad table manners or they are not his type. One stormy night a young woman drenched with rain seeks shelter in the prince's castle. She claims to be a princess, so the prince's mother decides to test their unexpected, unwitting guest by placing a pea in the bed she is offered for the night, covered by huge mattresses and 20 feather-beds. In the morning, the guest tells her hosts that she endured a sleepless night, kept awake by something hard in the bed that she is certain has bruised her. The prince rejoices at her bruised back. A huge wedding takes place in the palace. The prince couldn't believe that he found his true princess. Only a real princess would have the sensitivity to feel a pea through such a quantity of bedding, so the two are married. The story ends with the pea being placed in a museum, where according to the story it can still be seen today unless someone has removed it.
Recently I did something vaguely similar. I put another mattress on top of my mattress and box spring. And apparently the flexibility of the two mattesses combines to make a somewhat unstable platform which sometimes threatens to slant too much and roll me off the bed.
So I wonder about the stability of three mattresses one on top of the other, and four mattresses one on top of the other, and so on.
So how stable will ten pillows one on top of the other be, or twenty, or thirty or forty, and so on?
If the protagonists needs a pile 200 pillows high to survive his fall, but the pile keeps sliding down and collapsing whenever they try to pile higher than 100 pillows, he will be doomed.
In my opinion, the protagonist would be much more likely to survive a jump into a pile of pillows from a ten meter church tower than from a hundred meter tower.
And if he lands on a flat topped pyramid (or half pyramid leaning against a church) much more than about ten meters tall, his landing is likely to cause the pyramid of pillows to collapse and spill out and he might get buried by pillows during that collapse and his friends might have to frantically dig him out of the pillows before he suffocates.
So I can imagine a story where a technological or magical time traveler keeps going back in time to the protagonist's jump off the tower, each time getting the people to build the pile of pillows a different way in the hope that this new arrangement might save the protagonist.