I like both of them a lot :D Felicity kind of prefers body language and doesn't speak much so communication between her and Regan wouldn't be much of a problem. She'd probably be interested in Regan's martial arts skills, as she's mostly just self-taught and not refined or pretty at all in her fighting or self defense.

As for Antaros, Felicity would be totally interested in his history and would probably respect him a lot because of his age, so if they ever met she'd probably pester him with questions and annoy him to no end xD