I feel like we could have the outfits Ivory Bird, Red Queen and I think it was called Yellow Butterfly make an appearance once again. Those are jin, gon and yun locked outfits that I have not seen in the store in quite some time. There was also a male-only outfit at the beginning as well - I do not own a male character so I cannot check the name. We had them when the game came out, but since they were removed they have not come back at all.
Could be a nice to have them instead of having not-that-old event outfits return.
But if we are looking for other outfits I would definitely not say no to Lunar eclipse, Secret agent-since the way to acquire it has been removed from the game, Pure white seductress, Lycan heart, Breezy (the original one or a customizable one, not the Snapdragon recolor with the ugly tights that ruin the outfit) - I have not seen this one return since forever.