For starters, standard harem garb!

"Alright, so what colors do you both want?" Sothis asked, rubbing her hands together gleefully.

Dorothea raised an eyebrow and considered. "...I think... Red suits me best..."

Manuela pouted. "Aw, that was my first pick too, now I'd feel like I'm copying you!" she noted.

Sothis giggled a bit. "Hey, you can both have red, no one owns colors!" she told them.

"...alright then, two reds please!" Manuela chirped. Dorothea nodded in agreement.

Byleth hummed, and told Sothis, "Alright then, I wish that they both had exact versions of your harem garb, only in red, and in their sizes, obviously. Also, they should both be subject to the previous wish, with the girls able to customize them. Oh, and fix those clothes you just tore while you're at it," he concluded.

"Consider it done!" Sothis grinned, snapping her fingers, and her magic swirled around both women. Their clothes vanished, only to reappear folded neatly besides them, along with Dorothea's upper garb, mended. Then the harem outfits appeared over their nubile bodies. The veils, the jewelry, the fine, transparent silk, all there.

"...huh, this is actually pretty comfortable... If a bit embarrassing..." Dorothea blushed slightly as she looked over her form in the outfit.

"Yeah, these do look good~!" Manuela purred as she admired herself and Dorothea.

Sothis clapped and giggled. "Bet you both would have your number of fans skyrocket if you performed in the Opera in those outfits!" she cheered.

They both flushed. "Yeah, not going to happen any time soon!" Manuela replied, Dorothea nodding in agreement, and Byleth allowed a faint smirk of amusement to show.