Great story so far!

I think it'd be fun if he ended up in someone's butt while they riding at some point. Either under Leonie on a horse, or preferably under Ingrid while she's on a pegasus.

I also think it'd be great to get Dorothea and Petra involved. Petra always called Bernadette "prey", could see her doing same to tiny Byleth whether that means trying to pin him under foot or trying to catch him in her mouth. Maybe then Dorothea can take him from Petra and keep him safe in a bra cup under one of her boobs or something.