Hi!
The bunny girl costumes are part of the Bunny Lounge dream that is available to everyone. You can access it through the Dream Pal app on your in-game phone.
The maid outfits for Lyriel belong to a bonus dream with her available
for our Patrons, along with another bonus dream with Rae and Cait. You can find the bonus codes for the dream in this post https://rift.ink/3Tsqgnu
As to the costume system, we currently have no plans to implement that. Although there's a lot yet to come!