Well, it would be a nice consistant income if they haven't any other immediate use for her. It would also depend of course on how quick Cartour want their boat back. Stena would probably view Nordica as inferior to Superfast X anyway but by most accounts, she has better facilities than Epsilon. She is also well proven on the route, although probably more expensive to operate.
Actually, I'll continue this on the discussion board: Ambassador/Nordica/Malo: Where next?