Dunno, Bylass' regular outfit is pretty "obscene", might actually rule it as more since Sothis' outfit has the ornate ancient culture thing going for it.
Rewording the gist of what a redditor said, "I can't take seriously any scene Bylass is in because when you plop her next to all the other characters she looks generally outta place for the setting or like Edelgard's slutty girlfriend."
Aren't you the one who is the happiest!?This is war!!Obscene?To have the Professor be in such an obscene look, the Church is evil after all!It's quite divine.Not bad.Oh, how marvelous!You! You!I've bestowed upon Byleth a divine outfit after encountering the Divine One.