Can swap out velkas rapier for ricards rapier, especially if youd like to buff the weapon. If you do not want to buff your weapon then there is no need for a fourth attunment slot and only three would be ok.
can swap out the painted guardian leggings if the look of the boots bothers you. I suggest maiden/antiquated skirt as an alternative.
The moonlight great sword is for her knight summon assist. As a cosplay of her knight summon I suggest the silver knight set plus the elite knight helm. but the armor switch and the moonlight great sword are entirely optional