I see no reason that 'elite' recipe outcomes need to be limited to having the special ingredient being singular.
The pillow example could work with 1 majestic feather required to give the elite output, all 6 required or even a spectrum of outputs depending on how many majestic feathers were used. Both the player and the game should be able to handle this without any difficulty.
I would recommend that their be only one type of input that uses rare ingredients on each recipe and only one elite output, and I think that having all of the target ingredient being rare is the best way to go as it would encourage stockpiling the rare before crafting.
Here is an example
Normal
Lumber wood Figurine: 3 branches, 1 woodblock, 2 maple leaves
Elite
Tiny Lumber Tim: 3 broken boughs (rare branch), 1 woodblock, 2 maple leaves