I think Sophia can be a good unit if you favorite her for a few chapters or arena abuse her to catch up.
Regardless, What about the Experienced Mercenary type; The guys who've been working for a while and know a lot about life, normally shown through their supports.
Saber? (Haven't played Echoes, but he may be a smart guy in it)
(Haven't played 5, can't think of one for 4)
(Haven't played any new FE past FE9)