imo the very fact that your own definition of "very simple and easy to edit in place" apparel became increasingly expansive as you worked through your thoughts… demonstrates the core issue here.

even though lots of apparel is really simple (and I'd love stuff like auras and flowerfalls to help fill out the negative space around my ancients in a way skins/accents by definition can't!), the boundary between what is/isn't simple apparel turns out to be way blurrier than the boundary that is "no apparel, period"!

this is something that i think could conceivably be fun to revisit once every flight has an ancient, but along the way i'd much prefer that staff stick to their guns so that they can continue their current/chosen pace with releasing ancient breeds.

ALL THAT SAID, I have seen an iteration of this idea that proposes an entirely new category of (not-)apparel that is "foreground items," which stuff like flowerfalls would be categorized under and which would be allowed on ancients. a built-in division like that is something that i think could totally work long-term.