How about Jessy Schram for Christine Vale?
She played Hannah (Logan's girlfriend) in Veronica Mars and Susan Davis in the Jane Doe film series. She is a bit too young, but that's not really an issue in the 24th century since she could be forty and look like twenty.
She looks hot and can sing too, perfect for when Riker plays his trombone.
Speaking of which, why hasn't he done so yet on board Titan??