I'm all for this happening! Mordred has been a little more open about herself as a person lately, but won't give out her real name to just anyone. But with some work I'm sure Hikaru could get it out of her eventually.

Anyway, getting there would likely have to involve some situation where Mordred is happy or mad enough to speak aloud about her past and connection to her father. Some stuff that could bring that up includes being confused for Saber, something that allows her to feel pride in her blood line, or just plain old complaining about how much her past sucked.