Would love to see special/dedicated dialog for when the girls are in dominant sex positions.
I feel like I've noticed the odd line that will acknowledge having a dick, or not being the one penetrated, but then they use a lot of the normal lines during sex, regardless of dom/sub. I think "dominant lines" could also work well for when you let the heat max out and let the day roll over.
Or perhaps an item that changes their disposition to give them more dominant/aggressive dialog/personality?