So since Amaya’s wearing Mallory’s old Aragon top, which was then used for Marilyn, does that mean we can expect maybe some pieces from Mallory’s Seymour and Marilyn’s Cleves to resurface for Amaya?
It's possible, but we'll have to wait and see. Each design puts weight (both literally and metaphorically) on different measurements, so while their measurements and sizing match up well in the ways that work for Aragon, the same may not be true for Seymour or Cleves.
For instance...open skirts, like Aragon and Howard, primarily rely on a waist measurement. The weight is held there, and when discussing alterations it's quite difficult to alter the waist without throwing off the shape. Hip width and length measurements are also needed, but their impact is less crucial. However, for Seymour the hip measurement is significantly more important, especially in the US where the Seymour skirts have often been fit more tightly in the hip, and the waist is actually less crucial since it can easily be altered and ends under the bodice. And for Cleves, shorts have several more measurements and points of contact, so the waist, hips, AND girth measurement all come into play. And that's without even talking about the tops, which are almost always more complex to refit!
So, yes, it's possible, and I definitely wouldn't be shocked to see Amaya end up with some additional costume pieces from Marilyn or Mallory. But it's certainly not a given, and I'd be quite surprised if she got Mallory's full Seymour and Marilyn's full Cleves - just a skirt or jacket is more likely than both full costumes!